It does, cause youre citing potency.
Beyond that, yes, the newer classes tend to be disproportionately stronger than legacy classes, but no where in the ballpark how BLU would work on 1:1 translation. There is no skill in the game outside of BLU skills which can wipe out 50% of tankier monsters HP in 1-2 hits in dungeons when synced. There is "Oh yeah, DNC is somewhat stronger than the other classes," and "BLU just be destroying things." Gets worse when you understand HP snapshotting on things like Missile and how two BLUs can literally kill the tankier monsters in 2 seconds.
Youve got better faith in the player base, but seeing how the arguments and thought processes have gone in the past threads as well as tangentely related topics, the immediate response would be "TY SE! We love you"...and then 3 weeks later "SE why you still punishing BLU! Why these exceptions! No other class has this issue at 'x' level" and thatll turn into threads such as this where "What can we do to unlock the class and make it a full class." You read Reddit and OFs enough, you see a general trend in player rationality when it comes to balance on MMOs.
I wasnt talking about the mechanics side of it, but more of the theme side - I.E a caster who also engages in melee combat. Theme wise you can boil down the 3 casters (blue aside) to Basic B Wizard - Cast stuff and kill, Summoner is "I use pets to attack for me" (granted that due to balance they seem to be moving away from this and the emphasis to use pets - something I think is a mistake but I digress), and RDM is a hybrid Caster/Melee with more emphasis on the caster side.
They have their own theme of what they do. What I was saying in similarities is having BLU do physical stuff overlaps with what RDM does, though maybe inverted in that the focus is heavier on phys with bursts on magic. But then its a lot less a caster at that point and a hybrid melee dps.
Youd have to tweak potency values and give them access to a basic AoE early that has similar output as other casters. The point would be preventing BLU from using powerful skills in a low level dungeon that they theoretically shouldnt have access too. You already see this as is with other classes when syncing to level, so youd have to create a similar system for BLU.
I wouldnt call it separate leveling, so much as youd just have different stances that limit what skills you use in each stance for added benefits of having the stance on (tank would be threat gen and def/hp, DPS greater DPS values, Healing improved healing output for spells for example). This would allow queuing as a specific role and remove issues where you wouldnt want melee or healers to have a TANK LB3 skill as an example. The coding issue would essentially be preventing you from removing stances on BLU when in dungeons or instances. On the flip side, if you want to not have a stance and have your full kit, that option is available to you in open world content and in unsynced content. So you have the ability to use all of BLUs skills to do cheese runs if you want - just not in content that is synced.
I would want to avoid this because of it being a balance issue. The balance side is giving people the ability to address using a high risk ability by using other kits or abilities to work with it. If you tack weakness onto it, there is no real eason to use the skill, even as an execute because weakness stacks and persists through death unless its a complete wipe. Giving it a long CD + reducing HP to one would allow good healers to plan for the attack use in a fight and burst heal you back up, while at the same time discouraging an entire party from doing it due to how unlikely all people are able to heal the entire thing effectively with risks from raid busters.
Im still in the position that it doesnt have to be a full class and in doing so would require rebuilding it. The problem ends up being the same no matter how you cut it - Either the changes will be to minimal and BLU will end up being a must bring, or theyll be to drastic and result in needing to rebuild how the class operates. Much of what I suggested would work (on paper atleast from a basic stand point) and fixes a ton of potential power issues but in doing so would require a lot of reworking and rebuilding how BLU works. The other route of doing as little as possible and making some minor changes to skills and leaving it as is just doesnt work in FFXIVs end game environment unless you are gonna throw out balance or some of the philosophies that the devs are currently pushing (reducing the meta aspect of raiding, for example.)