"we don't need to make the enemies better in combat further in the game, lets just raise their numbers"
Basically, it's the same handicapped enemy you fight on easier difficulties, but he has more hp and does more damage.
This doesn't make it challenging, it's just as boring if not more because you're pretty much doing the same thing but for a longer time.
This is why I like difficulty systems in dynasty warriors games. Instead of just making them stronger, they also make the AI guard, try to break your guard, escape combos, do combos, etc.