Maybe I haven't played that much yet, but IMO, the AI is better in the third game. I don't even know what's so difficult about taking and repeating the AI that was made many years ago... sorry for the off-topic.
1) The AI of the 3 heroes is already outdated; it's worth remembering when they were released.
2) In the 5th game, you can play the same map several times in different ways, and the computer will make different moves depending on your actions.
3) The computer doesn't behave in a standard way; for example, instead of attacking a hero, it's easier for it to capture a castle and sit in it until seven days are up (I didn't notice this in the 3rd game)...
