My raid seems to be having problems with this specific mob either not spawning or despawning very soon after spawning. We petitioned it this week, but this may be the appropriate place. Each week so far on Aradune, we've popped this instance, cleared the majority of the trash on floors 1 and 2, then moved the raid to do the Taskmasters/Warden, cursed cycle, Rhag, then finished with XTC/High Priest. Basically, we work from the bottom of the instance to the top. As a result of the pre-clearing, the entire raid is able to move largely unimpeded to the spawn point of the Arch Lich after killing Rhag 2 only to find that he isn't up. I think we're going to be changing the kill order in next week's instance, but our worry is that something we're doing--- and not the kill order--- is causing him to despawn, hence the post. When it first occurred, we thought it was a random bug and didn't petition because there's not much of a point in doing so. This week, though, we're pretty sure something is going on, so we're trying to figure out what it is.