Are you sticking with civ4?

[Psyringe]

homm3 on impossible in a very small map is brutal, unless you go for cheesy necropoliss tactics or something

That maybe so (I wouldn't know since I always tend to play the biggest maps possible in any game I have), but I somehow doubt that the reason for that is the cleverness of the AI ...

 

[sherbz]

That maybe so (I wouldn't know since I always tend to play the biggest maps possible in any game I have), but I somehow doubt that the reason for that is the cleverness of the AI ...

No, the reason for that is purely and simply that the AI starts with a bunch of resources, you start with none. On small maps this makes it almost impossible for the human, even if you split your initial stack into individuals and try to cheese it by using a high level mage or ballista. Anyway, the complexity of HOMM3 is insignificant next to civ 4. The cleverest thing the AI does in HOMM3 is position its heroes in places beyond the reach of a human, so its very difficult to corner it and win\defeat its hero (unless you have some cheating spell like town portal or dimension door)