Ok. Well I see the point. One almighty demon army is more frightening than a myriad of smaller ones. I guess the cacaphonic and chaotic feeling of the Demon faction is more solid if the demons differ from each other very much (both in apperance and behavior).

But still, there seem to be only one evil faction in the game (I don´t know what you have in mind for all of those human factions though). Will there be some "evil" cult-faction? Some cult that indirectly act/work as agents for the Demon army or to some renegade demon/dark god/dark godess/spirit?