Actually, the gods do refuse to work together unless they can gain something truly worthwile from it. The new Daemons of Chaos codex and army book just reduces the dislike that the gods share a little bit, just about allowing daemons of different gods to ally together. However the gods still have huge hatred towards eachother and will not work together unless the event is truly huge (Black Crusade in Warhammer 40,000 or an Everchosen in Fantasy).