As combat with bosses typically is hindered by Defiance/Unshakable, in order to not allow players to trivialize the encounter, it in turn causes control abilities to be unreliable and pointless to bring along as opposed to more damage.
What if they scrapped that and worked CCs INTO the encounters.
Such as bosses that are highly agile and dodge a lot. In order to lock them down you need to immobilize or stun the boss to land attacks on them and they are debuffed to take more damage when immobilized or stunned.
What if a boss has a frequently used (not excessive but more than we can dodge reliably) kill shot? Blinds and interrupts prevent them from landing this dangerous attack. After every interrupted kill shot they are vulnerable to take more damage.
Bosses with a PBAoE effect or Fury if you fight in melee? Immobilize and Chill/Cripple to maintain distance. Again takes more damage if you keep them slowed and away from players.
The idea is to promote players to play smart and “do” the encounters, which in turn rewards them with more damage done, as well as better survivability.
Right now CC effects are long enough that by the time you burn through defiance stacks you are waiting a while before you can use it strategically again.
So build the adverse of the control effects and have players learn what CC to use on different types of encounters as a sort of paper rock scissors style of counter.
Pretty rudimentary, but thought it could spark more ideas.