The AI situations in Greece are always screwy for me. As KH, you can easily attack Korinth with no trouble from the giant stack. With Makedonia, Pyrhhos almost never attacks Pella, he always goes back to Epirus. As Epirus, no one does anything. I've played a game where I sent Pyrhhos and the starting armies to Italy, and no one ever bothered Ambrakia or Epidimanos for many, many years. It seems to work slightly better when the player isn't one of those three factions.