Next tank

[Carighan]

DRK/GNB are better at magical damage and they do higher damage than PLD/WAR which are both physical/magical damage focus

There's a few things wrong with that. DRK/GNBs aren't "better" at magical damage, they're just worse at overall damage resistance and self-reliance. GNB is alright as they still - for some nonsensical reason - have a superior Excogitation on a shorter CD with extra benefits but that's about all that is propping them up. DRKs is just sad now that TNB is no longer special or noteworthy in the face of Heart/Blood/Sheltron.

Then there's the damage output: While it is true that Gunbreakers do marginally more damage than the rest, the number difference is extremely small. And on #2 is Paladins. Overall and for all purposes, tanks do ~same damage, which makes little sense as they're not the same on the tanking side, even if you wanted to use that as the balancing stick - which is problematic in the first place IMO. It'd be okay if one tank trades a bit of resistance for a significant amount of extra damage, as their unique identity. Say if DRKs had to live with TNB instead of a proper short CD, and in return did 15% more damage (so 5%-7% from a DPS perspective), that's okay-ish. Weird niche, but still alright. But the other tanks need some different unique identity then, one not defined by damage.

(edit)
And sure, in theory it could be done that way.

Say of the four tanks:

* One is better at self-healing
* One is better at resisting physical damage
* One is better at resisting magical damage
* One deals more damage

That's a shakey balance in the context of FFXIV's combat design, but sure, workable. But that's also absolutely not how it's done right now, except the self-healing part on Warriors.