It is a morale slider now. I do not see any indication of an outright attack bonus for the AI anymore. When I tested this a week or so ago based on somebody's post I had very odd results. The interesting test was triarii vs. triarii. I seemed to get a better charge in (despite trying to match the AI's as best I could) and would win handily on VH. I saw some similar things with cav, but even with a winning advantage during melee my cav would usually rout early. So I think they scrapped the attack bonus for a morale bonus. That bonus is not always enough for the AI to win and is very sensitive to initial losses.

Easy battles take a lot longer. Probably because of increased morale improving defense in some fashion.