Dude.... I can run through the normal raid at 25 on my hunter and still do awesome. In fact, we had two level 30s with us who got downed before anyone else (all other levels 26, 27, 26). Myself and a level 27 brought us back form the brink of wiping on the last wave of oracles because everyone else got overrun. This includes me dipping and weaving through the swarms to get cleansed while almost dead, to find out the pool was gone, to then turn around and revive 3 people, and run back as soon as the pool respawned to get cleansed before dying. My point: it is very LARGELY skill and not level.