This is something that has just started recently for me, taking advantage of JJ and levelling some alts.
Whenever I try to use the Wyrmrest Defender to be able to kill the quest mobs - my screen freezes and I get the beach ball.
Similarly, I went to do the quest where you ride the goblin … uh… lumberjack, and there was a LOT of choppiness whenever I hit an action. Same kind of screen freezing - not crashing, but a brief and noticeable stall.
I’m on a M1 Mac Mini running Big Sur - activity monitor doesn’t show anything using a lot of resources.
This is a pretty recent development - I have done these quests on at least two characters previously, with no problem.