Nothing is really taken into account in auto-resolve. I'm sure you've noticed there is a certain amount of rock/paper/scissors to the units in this game. If you put an army of 10 armored hoplites on the field in phalanx formation, and I had an army of 10 upgraded forester warband on the other side, you'd probably be dead to the man before you could get to mine. None of that is figured in when the game auto-resolves a battle. It's strictly a number crunch with a lot of randomness thrown in.