but they are slow and smart players will usually have their archers destroy oncoming siege towers long before they ever reach their walls
Huh? Unless their arrows are flaming or are the size of a man, I can't see how arrows will destroy a large wooden siege tower.
Also, both Archers and Halberdiers share the "unique" formation Skirmish, albeit both are actually different. I think Halberdiers need a new name for their formation.
Otherwise, nice. Especially nice to see that you're keeping magic still somewhat under wraps