I didn't bother to read the posts on this mob, but nearly lost my wizzie when the three spawned and attacked him. Guess he had just set off an AE nuke, and they didn't appreciate it much. Did manage to get the evac off though, so no deaths on this one.
I gathered my wits and read the posts and headed back, expecting the spawns and was ready to root them from attacking me or the healer merc, but they never did. Apparently the first time they spawned must have wasted them for him. So he just went down, ever so slowly, but I took him down with my druid, wizzie and the tank and healer mercs.
Got the Belt of Opalescent Seashells, which is a nice upgrade for my chars, even though it's recommended for level 90. They have some weak spots in their gear.