Better let statistics speak for themselves. Here's a collection of random raid stats from the PvP server:
Molten Core:
http://realmplayers.com/RaidStats/RaidO ... Raid=19011Bosses: Rogue, warrior, rogue Trash: Rogue, rogue, warrior
http://realmplayers.com/RaidStats/RaidO ... Raid=18990Bosses: Warrior, rogue, rogue Trash: Mage, mage, warlock
http://realmplayers.com/RaidStats/RaidO ... Raid=18968Bosses: Warrior, rogue, rogue Trash: Warrior, rogue, mage
Blackwing Lair:
http://realmplayers.com/RaidStats/RaidO ... Raid=18972Bosses: Rogue, warrior, rogue Trash: Mage, rogue, mage
http://realmplayers.com/RaidStats/RaidO ... Raid=18932Bosses: Rogue, rogue, rogue Trash: Warlock, mage, hunter
http://realmplayers.com/RaidStats/RaidO ... Raid=18892Bosses: Warrior, rogue, mage Trash: Mage, mage warrior
And then for average performance of players in Molten Core, only bosses:
http://realmplayers.com/RaidStats/Ranki ... &realm=NRBTop 50 has 1 hunter, 2 mages, 17 warriors and 30 rogues. Note how a warrior is on spot 2.
Average performance of players in Blackwing Lair, only bosses:
http://realmplayers.com/RaidStats/Ranki ... &realm=NRBTop 50 has 5 mages, 15 warriors and 30 rogues. Note how a warrior is on spot 3.
Finally, average performance of players against all raid bosses currently on PvP server:
http://realmplayers.com/RaidStats/Ranki ... &realm=NRBTop 50 has 1 hunter, 2 mages, 17 warriors and 30 rogues.
So there you go. Warriors are certainly just as valid a DPS class as the "pure" dps classes.