Exterminieren
Banned
I've had this theory in my head for a while now that the eShop infrastructure doesn't currently support direct DLC code redemption. The Wii U versions of games have been left out of all the pre-order stuff thus far, with Rayman Legends being the only exception (which hopefully means that it's being updated prior to its release), and I think this also helps explain why there aren't any season or online passes on the system, too.
One would think with Rayman Legends coming out two months prior to Arkham Origins that WB would be able to offer it, but perhaps they're playing it safe for now.
Didn't RE:R have some pre-order Wii U DLC of some kind? I think I heard something similar to that.