Just like SoaSE the AI is pretty lame
Was just doing a tournament in single player and we were losing, even though it had been a close game the first 30min. And then I realized why. All three of my CPU allies were just sitting in town not doing anything. Even after the enemies pushed me back into my camp my allies would still just sit there and not attack or do anything.
I don't know what the problem was and my only guesses are one of three things: The enemy was 6-7 levels higher than they were, all war effort upgrades were purchased, and/or they ran out of ways to upgrade themselves through the store. In any scenario it's all a pretty lame reason for them to stop helping.