Bridge battles are your best friend should you fight them beyond walls. Put lots of spearmen at the end and watch a horsey massacre. I also recommend using units with the effective vs armor trait like sword staffs and Halberds, they are great at taking out the hvy lancers. I also noticed alot of times that if you take out their general, they get a huge drop in morale. Example: General runs across bridge to waiting spearmen and became the first to die. All other units including Heavy lancers bottled it soon after engaging.