Fascinating post, Puzz3D - seems I knew about the "nerfs" but did not appreciate the point about morale in MP. I've noticed that in SP, armies without command stars are fragile and can sometimes unexpectedly rout within a few seconds of a decent AI charge from a strong AI army. So I think I can understand the problem in MP now. A +4 morale bonus sounds about right.

But I think the SP model broadly matches my intuition - when it comes to cavalry vs infantry, who wins will depend on how steady the infantry is.