One time last week when I critted out and came back in game I was in the rift and immediatly went back in, the mobs where not doing any animations on my screen. They were all stiff and stuff, moving all straight and not swinging or anything, only when they used a skill would they make an animation.
Also no damage was being logged on the character in question, but the mobs were dying. It was pretty funny. I wish I could have had the boss, but then I critted out again and everythng was back to normal.
I also seem to lag only on one specific character and getting the "you've been disconnected" message a lot. No idea why.
if you are multiboxing or alt tabbing or something that switches the client to the background, ive noticed the game drops the framerate a lot, this can be solved by unticking the "reduce background performance" box in your game options. A little warning, if you are running a lot of apps or clients this will significantly reduce your performance, but would make 1 boxing performance far better.