I'm not sure why having to manage all of that in 'end-game contents' is even a bad idea. Players are supposed to have SOME degree of competency in that level - that's to be expected. If they can't meet that expectation, then they should go back and try again after improving.
Furthermore, varied damage options would definitely lower the output of some healers who're used to 1 2 1 1 1. That's to be expected. But that's also SE job to decide how far low: will they do 70% out of full potential for keeping 1 button spam? Or will be 50%? 30%? 85%? Personally to me, I'll take any. Even reducing Dia DoT to 18s like old Aero II would've been a boon for such a 'simple change'. (just one from many low bar examples)