Ok to root out misconceptions...

Hard in MTW gave about a 10% advantage to the AI in combat but no morale bonus.
Expert gave another larger bonus to combat (don't know it because I never played Expert) and +4 to Morale.
Normal was just that.
And Easy was the opposite of Expert or Hard (never played that one either so I never payed any attention to it)

Seek out Puzz3D, he knows the right figures, but know that the AI certainly got a combatbonus at Hard in MTW. You can test it out by playing two equal units at each other in Custom Battle at both Hard and Normal.