Something I tried with Warlocks was also using Shadow ward to reduce the damage. I just cleared this one early this morning for the first time using the follow method on Non Heroic mode.
I tried Heroic last week but could not down first boss due to the healing effect and not having enough dps to brute force him down, it seemed that the healing orb was immune to something I was hitting it with, destro locks were my main dps.
This morning I dropped in my arcane mage when i cleared it, so now back to clear it with my hunter who still has the quest lol