#1 - Pet Pathing need I say more
#2 - killing enemy's standing in toxic substance during missions - when you kill enemy's standing in toxic substances in missions you get NO XP and NO increase in token % I have lost about 2-3 mil worth of xp because of this.
#3 - Mission times when it comes to server down. I have had the bad experiance of having 3 hours left being 90% done with mission still have not found objective and the server going down for it's 4 hour downtimes results after server comes up I log in my mish has expired that is a big issue imho.