AIK only RE5 and RE6 have fully fledged coop campaign modes. Correct me if i'm mistaken but ORC is more of a Left 4 Dead type of game with Resident Evil flavour and Revelations 2 i guess didn't have online coop or it was very barebones, with one character barely doing anything.
2P is indeed asymetric with melee stuns instead of firearms, but while it's true that the game lacks online coop the splitscreen is still the full thing (including the Moira DLC). Easily one of the best AA+ "girlfriend games" for that reason and many others, though I still had a blast replaying solo later.
Regarding ORC it's obvious that the game was taking cues from the hyper-popularity of L4D but it still works as a story shooter with linear missions organised in a coherent campaign with dialogues, cutscenes and scripted setpieces.
I don't want to shill it too hard since its reputation as an ugly duckling is far from unwarranted, but if you skipped it because you expected a L4D structure it's actually more of a regular story-driven shooter.