Another 3 class comp I thought of is furyx4 + feral druid. This could be prot warrior + 3xfury + resto druid for instances. This team seems like it could cut through PVE with great ease like the 5xpally group.
Fury warriors are hard to run for maximum DPS. There, I said it.

There is almost no reason to put in a warrior for a PvE team. The allure of the warrior is the mortal strike debuff and invulnerability removal for arena/BG.