Compared to some people, apparently, I found QC a piece of cake as far as coffers/quests/sneaking goes. Mainly because there's plenty of places you can get to when sneak starts to wear that you can hide in and recast. And a few places where the coffers pop, they'll be in a blind spot away from the Antica. My advice is to have your warp method macroed. That way if you do get aggro when sneak drops to open the coffer, you can get out quicker.