Swen has stated, in the other thread on this subject, that it's being looked into.
Unfortunately for the co-op players, it was something that got relegated to a lower point on the priority list. They had a finite amount of time to finish before launch, and only so much they could get done in that time, so they had to pick and choose what to prioritize.
Last edited by Jito463; 04/07/14 06:31 PM. Reason: Separated comments for clarification