First of all I want to say that I love co-op. The reason is that I like bots. Yesterday I played a co-op vs AI and the bots got pretty fed but in the end we managed too win. I think that the biggest mistake they do is that they don't stay together later in the game. They were almost never together. I suggest that they stay together more in late game and that only one bot goes to defend a lane if it must be defended (right now a few bots go to defend a single lane).