This hasn't truly happened outside of tryhard parser PF groups (that are relatively rare) since Gordias and maybe Midas. It was Stormblood and beyond that ultimately showed the whole "Everything is viable" spiel that is in relative MMO terms is quite true. Gordias was such a disaster and nearly killed raiding at the time because anyone who wasn't a HC raiding masocist gave up within a month of a3s and even the other end of the coin hated the tier because A4S was a terribly designed fight in a multitude of ways such as:
Gear check, certain unavoidable damage was way too difficult to survive through and the dps check was difficult if you did the mechanics as intended because healers had to baby sit people more then normal.
Paladin couldn't tank the fight even remotely as well as the other 2 tanks because of SE's gay "Paladin can't block magic" policy at the time, but this a fight where most burst damage is MAGICAL so what the fuck. Paladin's damage was also garbage so they made the dps check harder. I think Pld got a a4s clear like a month after the world first did once more gear came into the picture.
Nisi sucked if you did it properly because of server fuckery and little room for error, but you can also completely cheese Nisi via saccing 3 people every royal pentacle and just ignore the entire mechanic for the sake of more damage, so it is a worthless mechanic while also being the most dangerous thing there. If healers want to feel anything, they should do NISI properly sync'd sometime. The developers literally apologized for NISI because it sucked that bad.
Whatever makes fights more braindead is the best option when it comes to class choice, if we had a T7 again and we had the heavy debuff on anything that worked on slow moving yet deadly adds, whoever could heavy the adds the best would be taken 100% because heavy kiting is less effort and more damage then actually doing that mechanic as intended.