There aren't any classes, at the moment, that use a stat for cross purposes. There are classes/abilities that swap stats however. DEX is specifically listed as modifying ranged attacks so, unless that were changed to apply on a class-by-class basis, there would need to be some mechanic that encourage/forces DEX stacking rather than STR stacking so as to prevent MNK/DRG gear competition.
By the way, I wasn't saying that STR and DEX should be *switched*. I was saying that the stance/trait should, effectively, apply ranged damage modifiers to melee attacks. All of the gear they would want to use would have DEX on it, not STR, since, if I had my way, I'd have STR do nothing except for increase Parry value. There would be no reason for FNC to use MNK/DRG gear because that gear has STR on it, which would be either a sub-standard or outright useless stat to have.
The problem with trying to treat it like Slow or STR Down is that there's a fair deal of difference between reducing incoming damage (with Halone, it's a fundamental aspect of PLD tanking: 10% lower STR makes you take less damage; the Slow does it, as applied by a DPS, but that Slow suffers from DR very quickly and many bosses end up being immune to it; this is one of the big reasons why Haymaker is effectively worthless for WAR) and increasing damage taken from *all* sources. As it stands, the existing +dam mechanisms really only buff your own damage or that of a small number of other classes: WAR increases WAR and PLD, DRG increases BRD and DRG, BRD (with a song that they don't even keep up all the time) increases BLM and tiny bits of a couple other classes. With the exception of the BRD, the +dam mechanisms exist as a self buff with a tangential benefit to someone else: you don't use them so that other people benefit but rather so that *you* benefit. This limits the maximum contribution that a single class can provide to a large number of people by restricting it to only certain classes.I was treating Reveal's debuff to have a similar value as Feint's Slow, Rage of Hallone's STR Down and so on (and unlike Feint, Reveal would do no damage, so you essentially "waste" a GCD applying it to increase raid DPS). The debuff's value would be more determined by the percentage, which is why I left that undefined. When I originally conceived Reveal I wanted it to become a single-use debuff for FNC and RDM and a stacking debuff for Mystic Knight though MTK's soul crystal mechanic (using the stacks more as a threat modifier for MTK rather than to further increase raid DPS while MTK is tanking).
A global -resist debuff would either need to have a really low contribution number or have a limited uptime. As a kind of support CD, it could easily work, but I don't see that as part of FNC but rather RDM. The "support" aspect of a class/job pairing doesn't really appear until you get into the "job".
As to having Reveal, which you list as a functionality of the class rather than the job, do *completely* separate things for each, it pushes design credulity a bit. You want to have an ability be a single stack group-wide damage buff for one job and a stacking, personal enmity buff for the other. It's like *possible* for it to be done as such (SCH changing the summon spells to something completely different is pretty good precedent), but it's a really inelegant solution. It would be better for it just be 2 separate abilities for each job.
Also, using a debuff as an enmity multiplier is a really wonky mechanic. Even if you use it as a resource to be consumed, it still creates a really weird construct where you have a longer time frame before you actually generate reasonable threat (recall: the other tanks have to get to the end of their combo to generate truly effective enmity generation). If it stacked up and wasn't consumed, you'd then be creating a construct where you start off with weak threat (which is when you need it most) and, only after the fight is already 10-20 seconds deep, work up to having useful amounts of it (which is when you need it the least).
There's a really good reason that enmity multipliers are always passives or self-buffs: doing it any other way is simply makes a tank *drastically* less effective.
I actually changed my design a *lot* from what you originally posited, mainly because there was enough that I didn't agree with as part of what you wanted me to fill in around, like having a 2 separate "base" combo attacks to create the separate trees, that I didn't feel comfortable working within those confines. I also pushed Magic Weapon, as it applies to RDM, through 2 other names/iterations and gave Magic Sword to MYS. I actually came to agree with Marta that an enchanted weapon makes less sense for RDM than it does for MYS; it makes more sense for a RDM to cast spells as part of stabbing someone than enchanting their weapon with magic (which is pretty much the MYS's entire schtick).An alternative would be Magic Sword reacting to whichever debuff was placed on the mob via the Soul Thrust => Spell combo. If the mob has no Burn/Frost/Shock debuff, Magic Sword cannot be used. If the mob has Burn/Frost/Shock, then Magic Sword deals damage and takes on the elemental property of the debuff. You could even have MSword consume the debuff if you want to add a "skill" component.