I'd have to say the Draenei. At least in appearance. The whole fleeing from some bigger evil has been done before, but like that matters. Everything's been done before.
The way the Worgen came into the world and work as a faction seem kinda original too. Unless I'm mistaken, I really haven't seen werewolves brought to the world by night elves and then spread as a plague in an isolationistic country to be brought into an alliance with dwarves, gnomes, elves, space goats and humans after being attacked by zombies. Weird long sentence.