Advantage comes with numbers and quality. If enemy has more men with bows than you, you have to try to engage them in melee as fast as possible and if AI understands this it can take good position and make you fight for high ground. Now you can just take high ground and wait AI to come there, even if AI has more ranged fire power. Im just saying if scripting got better the party with more firepower has advantage. I think range should be increased and battle maps should be smaller.
I think the problem with archer is bad scripting for AI right now. If we could play multiplayer battle and had more archers you would have to attack me or I would shot you down with my archers. I know how to use them in the way that you cannot catch them. I would shoot you once and retreat to higher ground behind my melee. Higher ground bonus is bigger advantage than you having more melee guys.
This would make you having archers as tactical advantage not as damage dealers.