Since the changes to VIT, tanks have so much HP that with proper CD use it's so easy to survive without tank stance, it's also easy, maybe less so for DRK than the others, to hold hate without tank stance.
Because of this, outside of mass pulling 4 man dungeons and some hard hitting tank busters in ex primals and savage, I basically never use tank stance anymore. It's started to just feel like an easy mode button, the only time I ever lose hate is to tanks who are using tank stance (who are basically just gimping their damage because I'd tank fine if they weren't doing it).
It's making me feel like tank stance should just be removed and replaced with an extra CD because they are just a waste of a hotbar slot most of the time. I get that it helps new and under-geared tanks and for WAR it's kind of rooted into the job. But I think these things could be worked around.
PLD: change sword oath to enlight (same effect just a different name) make shield oath no longer a stance but a CD, remove the damage penalty and just make it increase enmity and reduce damage taken. This makes shield oath more useful to experienced players while still keeping it helpful to under-geared or learning players.
WAR: remove the penalties and buffs from defiance and deliverance and just make them give access to the different moves and tweak some of the moves, unchained = increased parry, healing received and enmity generation, fell cleave add effect increase crit hit rate for 30 seconds. This would lessen the gap between defiance and deliverance on dps allowing WARs to use their defensive kit without feeling like they're sacrificing huge amounts of dps.
DRK: similar to PLD, make grit a CD and remove the damage penalty and grit requirement on souleater's HP drain, change the dark arts effect on power slash to increase damage instead of increase enmity, making the potency of a DA power slash combo higher than a DA souleater combo while keeping an unenhanced power slash weaker than a delirium combo, the trade off then being enmity and damage from power slash vs. hp and mp recovery from souleater. Grit would then serve the same purpose as shield oath in being helpful for learning or under-geared players while just being a buffer for experienced players and power slash vs souleater would have more of a trade off feel to it rather than a "I have to use this combo I don't want to use for the sake of keeping enmity" feel to it.