Supreme Commander uses the same engine. In theory, you shouldn't have any problems like that in Demigod, if you can play a 4v4 just fine in SupCom.
The funny thing is that Demigod requires more Upload than Supreme Commander because it sends data with higher frequency for some reason.
I suffer this problem too, im fully able to play Supcom 3v3 matches but demigod starts to spike in such games.
It would be great if they could lower the frequency back to Supcom or even wait addional 10ms more till next data is send.