Can't say how to do it with 5 shaman, but with a pally it's AOE, hit my shield buff with BoS on, count to 10, and then open up on him with everything. Last night I basically skipped clearing the area around him, ended up pulling a few other things with the fight, and everything was fine. I had problems with the bosses until I hit 45. Pally is at about 3k life right now with 53% physical damage reduction.

How's the witch-doctor boss? Can you burn him down without the spawns giving you problems?

The only good thing is that the 4 cobras at the end are 100% optional. I still can't beat them without someone getting killed.