the reason why tanking is my favorite role is because tanking well takes so much subtlety and game knowledge
anyone can be an okay tank in FFXIV (for regular content, at least). you hit all the enemies and press your mitigations one at a time and hopefully things die before you run out of them. in boss battles you point the boss away from your team so they don't get cleaved and push your "take less damage for a very short time" buttons when the big tankbuster marker appears. simple enough stuff!*
but being a great tank? that's more complicated! for example, here are things that I constantly think about as a tank that I never think about as a healer:
- party composition - if all DPS are ranged, then I have a LOT of leeway for where I can park the boss. but if there's melee in the group, then I have to be mindful that I don't stick the boss in an AoE puddle, or some other place out of their reach, and I make an effort to move it as little as possible so their positionals don't get thrown off
- (and comp matters doubly so in ARR dungeons - for some terrible reasons, some jobs get their AoE WAY later than others. it's Brayflox's Longstop, and both DPS are dragoons? sorry y'all, we're doin baby pulls. both are rDPS? HELL YEAH ALL THE WAY)
- how much to pull in general - how long did it take for the party to kill that last pull? do I have enough mitigations left over to go big on the next? does the healer have enough resources, or did they seem to be running on fumes? as a healer I pretty much shrug and roll with whatever everyone wants to pull - as a tank, I have to make those decisions!
and of course this isn't even mentioning stuff like Arm's Length being mitigation, or how you can use Provoke to get a faraway pack to bunch up and run towards you for easy pickup, or how you want to pop Sprint before you aggro stuff so you can get 20 seconds of it instead of 10, or how you'll want to shuffle around a bit to make mob with big hitboxes bunch up so your DPS can hit them all, or how you can hide behind a corner to force ranged mobs to run to you, or how you can make the mobs in the 83 dungeon's final pull come to you instead of dragging your party through the death stompers...
also, I feel like, as a tank, the metrics of how well you're doing are a lot harder to see than as a healer. as a healer, are you keeping people from dying to unavoidable damage? (emphasis on unavoidable.) if your party is eating vuln stacks like candy, are you making An Effort to keep ahold of their child leashes? party health bars at least are very visible! but as a tank, it's harder to realize that your healers are stressed out because the tankbusters are eating 80% of your health instead of 40%, or your melee DPS is chomping at their bits because you've parked the boss in a place where they can't hit their positionals.
there's a lot of tank insight I've gotten that I only have because I played a bunch of other jobs and roles, and I just think that's super neat.
* I say that, but you'd be surprised at the number of tanks I've healed in lategame content who don't use mitigations... or point the boss AT the party.....
(fallen london stamps by