I was in a top raiding guild at Nostalrius.
Top DPS classes are: Mages, Warlocks, Rogues, Fury Warriors
Hunters are considered "support only". We only raided with 3 Hunters max, and there was still considerable whining that we should take even less as the above classes in T2 did much more DPS than Hunters. Hunters are not quite a pure DPS class in Vanilla.
We also had:
1 Shadow Priest
1 Retardin with Nightfall (
http://db.vanillagaming.org/?item=19169#wh-comments)
1 Balance Druid (commonly known as OOMkin)
1 Feral Druid.