BE arcane torrent is great when dealing with casters in close range, i.e. when you are melee yourself.
Goblins are great at the start of an expansion due to low haste values and the extra 1% haste they have. The rocket jump is a live saver, but harder to manage while multiboxing.
Undead: it's an extra trinket vs priests, warriors and locks.
Orc: the extra spellpower racial is pretty much a trinket, and reduced stun lock effects are awesome vs rogues.

I'd always go orc warlock myself for pvp.