I suppose this thread is an appropriate place to throw my ideas in. I won't toss out potency and mitigation amount since I am no game dev. however the concept is more what I'm trying to pitch:
If tanks were required to be in Tank stance in standard content (be that raids or dungeons) and the "rotation" revovled around mitigating damage. We have seen some implementations with this concept in mind with inner beast and WAR beast guage and PLD with sheltron. I recently created a post regarding these changes and what would be required to implement them, and I do have an idea in mind on how a few of the tanks would function under this.
For DRK they would be more along the lines of "health shield" tank based off TBN and would generate a health shield in some way throughout thier combos so while primary threat target this recource would be used to ensure survivability of tank Buster's auto attacks etc. however with dps stance active (grit off in thier case) this shield recource can be expended on dps skills so that tanks like myself who enjoy dealing damage still can assist toward burning phases, dps checks and the like. This also plays to the DRK style of "spending health" to do damage. An additional skill can be thrown in that procs upon taking damage so that unavoidable AOE's aren't necessarily taking away from thier damaging tool once the player is hit.
WAR could actually play similarly to it's current state with this concept in mind. Just increase the parry rate while under Defiance a large margin and have inner beast do what it does currently with higher mitigation or increase max HP to fit WAR theme. Throw in more skills similar to upheaval that scale off hp so that the tools usually used to mitigate damage in tank stance still have relevance when out.
I unfortunately do not have any ideas for PLD, since I am very inexperienced with it, but I'm sure a similar design could be made for them too.

TLDR I agree that Tanking is a bit unintuitive and would like content to be scaled so tanks needed to be in tank stance when primary threat target and used same recources when in dps stance to deal damage