We are in the Heroes of Might and Magic V section... what does Heroes of Might and Magic III have to do with it?
That's why I'm comparing the fifth game with the third.
To be honest, playing against 3 AI opponents on a random map... I couldn't beat them.... At least not in the first 5-6 attempts... Then I started to get the hang of it and played better...
If the AI is too weak for you... play solo against several AI opponents... who are in an alliance...