I killed this boss no problem. I don't remember my team setup but the key is to watch the patrols. I left the Gate of Secrets (I think) and headed Right. Snuck around with the wall on my right hand side and was able to dodge all the mobs that side by just wall hugging. Once I got round the back of where the portal was I could see the boss. I waited. After a minute or so a patrol crept up the back of him. "Thank GOD I didn't go kill him..." I thought. I waited a few minutes for the patrol to head off back then went in and had all the henchies target the boss. Killed him in about 45 seconds, capped the skill...zoned out.
Personally I think the key is to watch the patrols so you don't aggro more than you can handle.
