I pretty much stand right by the enterance to HOR and go from there. I personally just stand right out in the open with Frost Aura from my pally up and just Bloodlust and DPS the piss outta him. I continue DPS even while Overlord's Brand is on and through all the frost damage from the dragon and whatever his huge spike damage move is. Just make sure your tank never goes below 75% health and you should be ok with just spamming AOE healing with whoever your healer is. I one shot this guy every time now if I manage to not wipe like mad on the trash before the cave.