Someone in every single job quest (no necessarily the quest giver) has the relic weapon. Curious Gorge wields Bravura, the BRD job guy wields the Artemis Bow, the bad guy in the SMN quest wields the Veil of Wyu, the rogue Sultansworn in the PLD quest wields Curtana, etc.
The difference is that in none of those quests is the individual that you're dealing with the leader of one of the major cities. The leaders are *supposed* to have unique models/weapons because it's one of the things that distinguishes them. Raubahn gets his unique swords and shield; Merlwyb gets her unique guns, and Kan-E-Senna gets her unique staff. I'm pretty sure that the sultana has unique clothes, along with the rest of them, as well. Also, Merlwyb couldn't be the job giver because she's not accessible outside of cutscenes, like the rest of the city leaders. She's too important to just stand around staring at people.
While it's not *impossible* for her two guns to be the COR relic weapons, I wouldn't say that it's likely unless the devs are willing to break what looks like a rule (the city leaders have unique gear to distinguish them).
As an aside, Yoshi pretty much said that any dual wielding that occurs is going to be single slot rather than 2 slots. Allowing for main hand and offhand weapons opens up a lot of really weird balancing problems (especially if you want the two to be interchangeable). The unique schtick of the COR relic weapon could be that, unlike every other brace of pistols out there, they have different models, but I'm pretty confident that the devs are going to have the pistols as single hand weapons.
On the the classes/jobs themselves...
Musketeer:
The animations that we've seen from the gun using boss in Pharos Sirius, as well as all of the gun animations that currently exist in game (Merlwyb draws both guns but only aims one with her offhand pistol simply kept down in the same position as the empty position; the Jade Fox only has a single gun during the GSM story), are all one handed. If you want to have non-gun using abilities as something of a baseline functionality (cards, items, dice, etc.) it makes more sense to simply have MSK be a single weapon using class and have the offhand exist for the secondary effects and/or special movements like fanning or pulling an item out of your pocket for certain attacks. It fixes pretty much all of the aforementioned problems with dual wielding without really costing anything. Plus, if you really wanted to get some dual wielding in there, you could include abilities like "Holdout Pistol" (off-GCD attack with the animation of you drawing either a generic pistol or a double of your existing pistol with your offhand and firing it) and "Dual Wield" (on-GCD, combo finisher, you draw a second pistol that follows the same visual rules as Holdout Pistol and unload both of them in the target's face) without causing weird gear problems.
For the attacks, I *really* don't see a well developed rotation. You have Hot Shot (which only makes sense to use once every 21 seconds) comboing off of Split Shot which leads into Last Stand (which is just flat damage). When you get to COR, you then have Detonator combo off of Last Stand for flat damage once again, which is strange not only because it's more flat damage combo'd off of a DoT but also because it's a 4th attack in a combo (of which there are none, probably for good reason since it sets up too much necessary contingency that gets screwed up if you miss or use a different attack). Assuming that you intend "Quadruple Shots" to mean that you get 4 auto-attacks per 1 (this is ARR, not FFXI; there are no "Double/Triple/etc Strike" status effects so you need to actually say "Increases the number of strikes per auto-attack to 4"), you'd actually be turning the rotation into Split Shot>Slug Shot(until proc)>Split>Hot>Last because of how insanely strong Slug's effect is (160 potency + 10% chance for 4 GCDs of 300% additional damage from the 83.33 potency you get from auto-attacks = 260 potency; 180 potency per GCD compared to the 140 you'd get from Split>Hot>Last, given how you have to use Hot Shot to access Last Stand and, as COR, Detonator so you're pretty much never going to actually get the full 21 seconds; you'll probably get closer to 4 ticks, at 12 seconds, which is what I went with; when you add Detonator, it actually goes up high enough to make Split>Hot>Last>Det viable, but, if you're using that, you're getting even less out of Hot than you normally would, which is going to drop the damage per GCD even more).
You *really* need to pull Hot Shot from the middle of the flat damage combo so tht it exists on its own like Fracture, shorten the DoT by a crapton so that it doesn't constantly get clipped, or put it as the capstone of the current Slug combo (I would also remove Wildfire from the combo as well and make the DoT cleave a static benefit, given the cost and how it's not like getting DoT cleaves on AoE spam is going to do all that much extra damage). I would also remove Detonator from COR since the baseline class *really* needs a straight flat damage combo that it can always access.
Providing Remedy as a baseline class function instead of a healer job specific function is almost absurdly powerful, especially given the instant cast self heals and other control effects provided. Being able to remove debuffs on yourself with no cast time and no CD as a DPS is *incredibly* strong. There's a reason that only WHM and SCH get access to cleanses; giving them to a DPS, especially an rDPS, is just a recipe for laughing your way through PvP (not to mention being super strong in solo/debuff heavy environs; the Det down debuff on Titan would mean absolutely nothing to a COR since they could remove it themselves instantly).
Assuming that you want Ironhide Ungent to not stack with Protect, I find it strange that you want to provide the full sized Protect to a DPS class. It's not something that is necessarily *wrong*; it's just weird, given that Protect/shell is a WHM thing that stands a reasonable chance of having it be one of the the unique things that a WHM brings to the party. It might be more interesting for it to be on a CD and provide an absorb shield to everyone within a given range (starts off only reducing physical and then gets the trait to apply to both).
The 25% INT debuff on Sniper Shot seems kind of large (and just having it apply to INT instead of INT and MIN is pretty strange). Virus, which is supposed to be the powerful stat debuff, is only 15%. 25% is reaching pretty high, especially since Sniper Shot looks like it's really intended as a damage buff, so it exists at something of cross purposes.
Chemist:
I'm not entirely sure I see the point behind Chemist getting a bag as an offhand weapon rather than just having them pull items out of a pouch at their side. It seems like you're only doing it because you want to have classical dual wielding and needed something to give Chemists other than a second weapon, which also begs the question of what the point of it would be. Your providing a stance that changes what gear you can use, which doesn't any precendent in game, and forces players to go in and change gear manually every time they change classes (since you don't load into a class/job with any stances up; you would have to swap to Chemist, activate Throw Items, and *then* you get to put your bag in that slot), as well as causing them to lose a slot if they ever change stances in combat or get resurrected. Swapping Mind and Dex makes sense, but the rest of it is just horrible (esp. since you're having it apply a global 2.5 sec cast to all abilities rather than just saying something like "adds cast time" which would allow you to vary what the cast time is, so that Remedy gets the same 1 sec cast as Leeches and Esuna).
The whole "Stash" concept is interesting as a *bonus* mechanic but forcing it to act as the primary resource for the entire class is just horrible, horrible design. You're completely abandoning the actual resources the game uses and applying a completely arbitrary one that is so heavily restrictive that players have next to no real input into it. Any misclick or overheal is going to punish you severely down the line, and, as far as resources are concerned, you are completely resetting their entire resource pool every minute so they exist in this weird set up where they have resources and options that dwindle very quickly and are then completely refilled so that you have the full suite of options again, for a short time. You're telling the player that you've already made the decision about what abilities they're going to cast and how often they're going to cast them without letting them actually choose (WHM can choose to use 12 Cure IIs or 30 Cures with the same MP; the devs set the costs, but the player still makes the choice). There's no choice because, even if you need to do a lot of high intensity healing (like on Caduceus with multiple stacks), you don't actually get to change how you consume your resources because it's the exact same allotment of casts that you get when you *don't* have to do constant high intensity healing. The only choice a player gets to make is with Mix, which ends up consuming resources faster for marginal improved benefit (it seems like you're actually saying that the first cast is used normally and the second gets a buff depending upon the first one used, which isn't really "mixing"). You're also forcing an huge level of micromanagement by providing different stash amounts for every single stashed item so that players have to watch 6 different buffs on their bar at all time, remembering which ones is which even with the numbers obscuring the icon amidst the rest of your buffs.
It's clear that you modeled Stash after Aetherflow but you have to remember that Aetherflow exists as a *bonus* resource rather than a fundamental action resource. Aetherflow doesn't *replace* MP; it exists alongside it as a secondary resource. The same needs to be true about Chemist (it should also be noted that, based upon this design, absolutely nothing could be done to improve the resource pool; if you run low, Ballad would do nothing, Ethers would do nothing; you'd be screwed until Stash came up again). Stash should be a resource that is generic rather than specific. You should be allowed to pull out whatever you need from your Stash because you're already making the assumption that the Stash is an abstraction (since you have an infinite number of X-potions even if you can only have 1 per minute).
If you're going to make it super important to Chemist (which it looks like you want to do), you should at least provide some modicum of importance to the DPS, similar to how Aetherflow is there for Lustrate/Soil for SCH and Fester for SMN. Swap out some of the more inappropriate stashed abilities that MSK gets (Stashed Remedy, Stashed Hi-potion) and replace them with abilities that would actually benefit the MSK/COR's primary role of DPS. Have Sleep Shot consume 1 or 2 stacks of stash (it's special ammunition). Throw in an explosive round that consumes a stack of stash to do a targeted AoE. Provide a stash consumer that restores some resources (which is likely what Chemist would end up using for resource maintenance). Replace Quick Draw with "Rapid Reload", which consumes 2 Stash stacks but increases attack speed by 10% for 10 seconds (and, because Stash is on a 1 min CD, could only be used once every minute). Make it so that Stash becomes more than just a healing resource that would probably just get ignored by nearly every MSK/COR on the planet. You'd probably also want to actually keep the number of Stash stacks constant for CHM and MSK/COR (you could change Pharmacology to be a bonus Stash recharge ability on a 5 min CD if you want CHM to have access to more or possibly an ability that makes it so that all of your Stash consuming abilities consume 1 less Stash for 10-15 seconds).
On top of fixing Stash so that it's a secondary resource rather than a primary resource, you have to address what the primary resource is going to be. You either need to decide that they will be using MP and be required to bring in Cure or Physic as a cross-class skill or provide them with a cast heal as part of their class (you could do this with Stashed Potion; similar to how SMN gets Physick, MSK/COR would be able to cast it without consuming Stash stacks, which they reserve for offensive boosts, but not get much out of it) that consumes either TP or MP. Since you want them using BRD gear, which means that they don't get PIE, you need to have some way for their resource pool to scale up as gear progresses. An option for this might be to provide Chemist with a 15 second CD off-GCD ability that restores the primary resource but can only be used within 5 seconds of scoring a critical heal (call it "Windfall Ether") so that critical hit rating acts as a form of piety for them.
With First Aid, I'm not entirely sure that you *need* to have Mega-Potion. If you change it so that First-Aid consumes a stack of Stash and have it apply the same heal to all targets instead of spreading it out, you get the value of multiple AoE heals (FA + Potion, FA + Hi-potion, FA + x-potion) for the price of a single ability slot.
Also, there's no real reason to force different potencies on the healing abilities for CHM and MSK/COR. You're having them be driven by MIN so, even if it were a cure with a huge potency, it still wouldn't heal for a really appreciable amount because they just don't have the MIN for it (especially if you give them a pitiful MIN akin to how WAR has a pitiful PIE).
Corsair:
As to the actual mechanics, allowing for the class to maintain 10% +crit, 10% +dam, and 10% +acc pretty much all the time is insanely strong, especially given that you're allowing them to do that *in addition* to the standard damage that a MSK would be throwing out. You didn't list a duration on any of them (that I could see) so they're, for all intents and purposes, permanent bonuses, which means that MSK needs to stack next to no acc (thanks to permanent +10% acc) and gets nearly 15% +dam compared to a MSK (10% from Red and just shy of 5% from Black). The debuffs that they provide with Leaden Salute really only place any value on the Red Card buff: people already stack acc until they can't miss and, even if they were short, would get a *minute* damage advantage out of the increase in hit chance from 97% (or whatever they had) to 100% (with 7% wasted) and I'm not even sure that enemies *have* critical evasion (unless you intended it to be more like a 5% per card increase in crit chance against the target, wherein it's still less than half as useful as the Red Card buffs). The 6 sec duration of White Card is really weird, given that every other debuff of the kind is divisible by 2.5 (the GCD). The only things that have durations divisible by 3 are DoTs (because that's when they tick).
You really need to either reduce the value of the cards (Wrath is 2% crit per stack; you could do 1% damage per Red Card, 1% attack speed for Yellow, and 2% crit for Black, which would keep them all at the same relative usefulness without letting them provide *too* much).
For Wild Card, the skill speed increase is horrible, so, unless you planned on providing a super weak option, you need to replace it with something more valuable. 20% +skill speed reduces the activation time by almost laughably small amounts (Selene provides 20% +skill speed with one of hers with 50% uptime and it's barely noticeable; it reduces GCD by something like .1, at most, which doesn't even translate into an extra attack over a 30 second duration). If you want it to be useful, have it modify attack speed instead of skill speed (so that it modifies the end value, like Greased Lightning does, rather than the base stat), though you'd need to fix the values. Since it doesn't seem like you're giving the cards any durations, it's effectively a permanent third card (at least until you use Leaden, which, the permanent duration of the cards,
Loaded Deck also seems kind of arbitrary given it's a stance that has no negative effect and would be kept up at all times (Cleric Stance and Defiance both have negative side effects so there is a reason for those class/jobs to run around without their stance on; yours is providing no reason not to). You could more easily implement all of the Loaded Deck benefits as Addition Effects that are only accessed while you are a Corsair, which would free up one ability slot for something that actually has a reason to exist.
A more effective implementation of what you're desiring out of Loaded Deck (if you really want it to be a stance) could be for it to apply a 20% -dam debuff and consume MP while active (or 25% increase in TP costs if you really want to differ from the BRD model, which acts as both the negative effect as well as the time limitation) and provide either the benefits you receive from your cards or some other ability contingent upon what cards you have to all allies within 5y (10% +dam for *all* damage dealers is friggin' insane so forcing people to stack to get the benefit is fully justifiable) so that, instead of having 3 different stances that all do something different, COR would have a single stance that can do multiple things while it's active. Of course, since you can have multiple cards active at all times, you're not really providing one of multiple benefits but instead providing the same benefit at all times, which probably needs to be addressed, which brings me to my next point.
You really should have a support class that provides the same support pretty much all the time. As it stands, you've got COR providing +acc, +crit, and +dam pretty much every time. Yes, you *can* elect to use it early when you only have one type of card, but there's no real reason to and, in fact, because you're having the cards provided by pretty much every attack, it's really hard *not* to. When I first read your idea, I thought that you could only have one type of card at a time, which would mean that you could buff either acc, crit, or damage (and, once again, you're providing a benefit that applies to *everyone*, as opposed to a subset, which is what all current support capabilities do, which is obviously intended, given how you can't have Selene's skill and spell speed buffs up simultaneously). There should be a choice of *what* the COR is going to buff rather than just *when*. A possible solution is to could restrict the number of total cards that you can have to 5 by having the total of 5 place the "Full Hand" de/buff on you that prevents you from getting more cards (you could right click cards that you don't want to get try for a different hand) and Leaden Salute could be made to only be able to be used while you have a Full Hand (like how WAR requires you be Infuriated). Depending upon what hand you're showing (2 pair, 3 of a kind, 4 of a kind, full house), you could get different benefits that apply to different groups. Either that or you could have multiple Full Hand consuming abilities, like a group buff, a straight up high damage attack, and an AoE.
If you do this, you would likely need to change Wild Card into something like "New Hand" or "Mulligan", which gives you a random assortment of cards equal to the number of cards you currently have. It could be reduced to a 60 sec CD pretty safely.
So, to sum it all up, here's what I recommend you do...
General Changes:
Get rid of dual wielding and replace it with a single gun.
Change Stash so that it is a resource of 3>4>5 (add Secret Stash II as a trait) that has offensive uses from MSK and gets additional healing/support uses from CHM.
MSK Changes:
Fix the combos: Hot Shot shouldn't be a tier 2 combo attack that's part of the flat damage combo if it has a long DoT duration; provide a full flat damage combo as part of MSK instead of requiring COR; provide 2 separate full ST combos instead of one 4 part, one 2 part that can turn into a 3 part but is only for AoE.
Remove stashed Remedy and stashed Hi-potion.
Add offensive/utility Stash consuming abilities (Explosive Round) and change existing abilities (Sleep Shot, Quick Draw, Drink) so that they consume Stash stacks (not all of those would necessarily be changed, just listing some that could be changed)
Reevaluated Ironhide Ungent (esp. Ironwill Ungent) and Sniper Shot
CHM Changes:
Get rid of gear changes as part of Throw Items.
Decide whether maintenance healing is intended be done through cross-class Cure/Physick or unlimited cast MSK Potion.
Add Windfall Ether (or some other resource returning ability that procs off of crits) in place of Mega-Potion.
Turn Hi-potion into a flat cast.
Turn X-potion into an off-GCD large heal that consumes Stash.
Change Pharmacology to Stash refill or cost reduction ability.
COR Changes:
Get rid of Loaded Deck and simply transfer the card gaining abilities as additional effects on all abilities. Conversely, have Loaded Deck turned into a limited uptime stance that spreads card buffs to all nearby allies.
Reduce buff value of cards. Get rid of +acc and replace with something more useful, like +attack speed.
Reevaluate all +skill speed buffs and/or change to +attack speed buffs.
Modify support capabilities so that they are not global and are instead specific to certain roles/class subsets.
Reevaluate card generation/maintenance/consumption mechanics and limit number of total cards at a single time (without limiting card type)