Well I have a level 30 Hunter and I was almost always the last person to die when I did the hard raid. It's not just about class but about play style. Also fun fact, in my raid group of four level 29's and two level 30's(myself included), on the Gatekeeper all the level 29's died after my fellow level 30(he was a Warlock) and I left the second portal and we had to defend the Conflux by ourselves. We succeeded.