Maybe it could apply a 12 second Slow to everything it hits, and also produce increased enmity. That way, you'd use it to get a pack of mobs on you decidedly, and since in most cases AoE tanking involves tanking mobs that are weak individually, hitting them all with Slow could perhaps considerably reduce their collective damage on the Warrior.

For those that think that doesn't make sense or go with the moves flavor, imagine that the enemies are disoriented and off balance after being slammed into by not only the axe blade, but the vortex of air produced by such a rapid, powerful spin. Or whatever other RP rationalization you require. =P

Though I admit, I don't really know how powerful Slow as a status effect is considered to be from a defensive standpoint in this game.