Problems with Heroes of Might and Magic IV.

There's no argument against a human player. But against the AI, its heroes rarely reach level 5. If you equip a level 20 hero with good artifacts, they can defeat a level 4 hero. I had a level 15 rogue defeat a dragon lord one-on-one :)

He might defeat one monster, maybe, but then it means that his skills are only developed in combat, i.e., when there are monsters that the hero CAN'T handle, then an army will be needed that won't receive any advantages from the hero's presence, and will most likely suffer losses...
P.S. The AI is certainly dumb, but not so dumb as to pit level 20 heroes against only level 5 heroes.