Why replace Stalkers with Assassins? What's the point? I only did that in the game when playing as Erathia because she has a chariot and you can organize a prolonged battle and eliminate high-level, low-initiative neutral creatures. There isn't much point otherwise; why do you need archers when you have Stalkers and Fury, which, with the right tactics, can transform into archers? You can even play the entire game with just them. When playing as the Elves, I never felt the need for archers. And as already mentioned, Fire Mages are the ones who decide the outcome.