Entrancer R`Ker in Fourth Gate is an interesting encounter at the moment. The golem outside of the door doesn't aggro if you engage the mobs in her room, so preparation for the fight is simple enough. The problem comes when you get her down to 20% health and she spawns a weak-minded guard. As soon as this occurs the zone crashes. I tested this twice yesterday and it happened both times, with the zone recovering within a minute. Hopefully this will be patched before the expansion goes live.