Like I said before in BfA theres no need, all bosses die in seconds, they don’t even get to do their abilities/phases most of the time.
In shadowlands I have done sanctum of damnation and sepulcher (most of it) in sanctum, the eye of the jailer dragging chains are ridiculous, it’s a luck fight, since they don’t hit you everytime because they miss, either they hit you at the start and you get pulled very slowly giving you time to react, or they hit you at the end of the fight pulling you super fast and in half a second you are dead.
KT needs you to leave another character outside the portal or the fight restarts, so either you can summon something or you are done, and sometimes it even bugs out and you summon something and it does not work.
Sylvanas has a mechanic where she throws you off the platform, so either you have something to come back immediately like a charge, or something like divine shield to avoid being hit by this.
There’s also the infinite fear loop from the guy that is torturing garrosh, and the damage deal by the fatescribe, those are dps check, out of that KT banshees and Sylvanas fights are the only relevant damage fights, you can survive them with some healing and killing the banshees.
In sepulcher, I don’t remember the name of the bosses, but there is one that summons like giant holy novas non stop, and they hit like a truck, but you can avoid this y being on a corner of the platform, the holy novas won’t hit you at all. And all other skills he use are not relevant at all.
Then there’s the giant mechanical spider, he has some orbs that explode and you have to deal with them, by activating one and then using cool downs to survive the damage.
Anduin is just a gear check, you have to bypass so he does not reach second phase because the adds hit extremely hard.
Then is the guy that summon sparks, he is another gear/dps check, if you don’t burn him fast enough you are dead in seconds.
Literally mechanics is the main issue, if they remove phases/skills like dragging chains,most fights are cake, it’s good that they will nerf them, that content is forgotten, and the actual mechanics are making the few people that wants to go (either to her mounts or gear for transmog) to just stop doing it since it takes lots of time or sometimes you can’t just do it at all and give up.