Same, I have the New 52 Skins Pack listed in my DLC, but no Harley Quinn Story Pack.

I got the new skins 52 pack but for some reason I don't have the harley quinn dlc

@IGWOO
It 's not important when you register the code with your steam account. The code is tied to the "Batman: Arkham Knight Pre-Purchase" (or similar) package and will stay this way forever. You could activate the game monts after release and it would still show up as "Batman: Arkham Knight Pre-Purchase" (or similar) at https://store.steampowered.com/account/

Yes, If you buy this game before it's released you will get the Harley Quinn DLC

Yeah, I mean when you send out the codes (A few days before release or whatever) it'll technically be a pre-order. Since we redeemed the code before the actual launch and pre load the game. I'm sure they'll allow preloading since recent AAA Steam games have had it. Anyway, since we redeem the codes before release, will we get the Harley Quinn stuff?

@IGWOO
The game will probably show up in your steam account as "Batman: Arkham Knight Pre-Purchase". Keys sold after release will just register as "Batman: Arkham Knight". The key actually determines which of the steam packages will be tied to your account.
So yes, basically the keys work like pre-orders in steam.

I'm not sure what you mean, we're selling Steam keys but we are not Steam.