A lot of high level tanks just genuinely prefer tanking over DPSing despite being more than capable enough to do both.
Still better than slashing debuff and damage down.
I knew this was bound to prickle someone.
There are plenty of alternative things that world-first progression tanks could be doing with their time. But everything has a time cost, and skill only comes from practice. More often than not, it's easier to stick with what you've invested in than it is to start off in a new direction. But I think that there's more incentive to swap off now than ever, given how badly the role has been neutered. The clear hangs on the DPS, not the tanks or healers. If you're looking for a challenge or the chance to make clutch plays, you just won't find it.
And to be honest, most examples of versatile 'high level players' that I can think of are melee dps, simply because of how translatable their skillset is, and because of how little ego they have invested in playing a specific role. Anyone can hop off and reclear on a different role, but relatively few are able to actually prog effectively on it.
You do have to be careful when adding mitigation to healers as it could make a tank's mitigation kit useless, unless you plan to make things hit alot harder. This is where you have the difficulty of balancing incoming damage with the mitigation tools available to both tanks and healers and the ability to recover said damage after. Swing too far in one direction and you can potentially cause problems that you might not have envisioned.
Tanks should have less defensive cooldowns and stuff like 10% armor, armor penetration or whatever should be part of the overall rotation.
Imo, a WAR as MT don´t even need real healer support and as OT, you can easily heal the MT or rescue some lowlife DPS / healers by yourself. The buffed shake it off is an insane medigation for any mechanics. Tankbusters will be taken with invul anyway.
PLD can heal himself if needed. Yeah, it´s not great for your DPS, but overall? Being even able to deny debuffs with your invul in every mechanic is just insane.
DRK´s blackest night needs to be atleast on point. Being the MR tank was a great thing, but got doomed into nowhere.
GNB has way too many defs and possibilities. To take care for teammates is fine, but it just feels like button smashing.
Tanks are way too strong and mostly you don´t even need all the defs you´ve.
Other games do it just fine. In fact, most have even less defensive abilities in general. Reactive heald, thorns effects, target able flat DR. Gimme my Ironbark dammit