One thing that really slows down my machine is the mass of text coming from killing large groups of mobs from other players. I really don’t care to see how much damage another player is doing in the field when I am just passing by. I would support being able to toggle this feature or it being grouped with turning off other player’s effects.
Secondly, I do not mind the screen shaking whenever I kill a mob, however when it’s a large pack of mobs in a dungeon it severely drops my FPS (from 60 to 5 FPS was the worst case). It also seems unnecessary when I am killing small mobs in the field. If it did the screen shake on Overkill/Elites/ Field Bosses/ World Bosses that would make sense. Maybe just another toggle for this would fix it.
I would throw in something about the number of particle effects, but I’m sure there are other posts.