I've won a 4 V 4 against 4 normals. I was playing with 3 other guys, but i got disconnected from my internet so the other guys got replaced with AI. I beat them by controlling the AI with the map commands. Just tell them where to go and they'll send their hordes there. The trick is to rush early game so they don't get the resources. Sooner or later they'll retake some, but by that time you'll probably have some tanks.