The underlying problem is that armour isn't good enough, so battles last barely any time.
I think this can be balanced a bit better in a few ways:
* Make armour provide much better protection against ranged damage, so that shieldless shock infantry are a more viable choice in the player's army, and can be used to break open shieldwalls.
* Make shields take
slightly more damage from arrows and bolts, so the player can eventually break shields with enough arrows.
* Increase the effectiveness of melee cavalry charges so if you send your heavy cav to attack a turtling enemy formation they can do better damage than now.
*
Reduce the amount of troops who use large shields in the game a bit.
Unfortunately yes. We need armor that functions more realistically against arrows!
And take the Glaive from the Khan's Guard.