I just did this quest last night at level 40 on all 5 shamans (all ele specced). I figured "well with all guys at level 40 and somewhat-decent gear, I should be able to handle this easy", but I still went OOM on all 5 right as the last 2 groups spawned (plus the boss). Funny enough, I stayed there and none of the mobs attacked the quest giver, he finished, I got the quest completed dialog, then I ran back from gy and killed the last few mobs and turned in the quest...the ring was a pretty big upgrade so I'm glad it worked out...I don't remember EVER completing this quest even when I was single boxing running the instance with others. Maybe if you have 4 melee and a healer it would be easier because you wouldn't have to worry about mana, but I even tried using windfury and meleeing a lot of the guys and I still went OOM pretty fast. I think I'm at a weird "in between" spot though because right now at level 40 (well, 41 now) I run OOM really fast on my guys, 2 pulls in an instance and I have to drink, its ridiculous). I have about 2k mana per shaman right now.