Lol the archers, which are tier 5, will of course have the upper hand if you order a charge from that far away. As hruza has said, You need to command them to move in formation as close to their unit as you can, preferably attack from one side at first so they can overwhelm the end of the archer unit and mow down the rest in a line formation charge.
Another thing that I have noticed is because all units are right-handed, the side you are shooting from matters. Infantry wield their shield in their left hand so if archers are shooting at them from the left, it will be blocked. In the case of your video, since it is just a test and there are no other formations to consider, you should move your sergeants in shield wall formation to your right.
In large battles, because the AI is ****, it is useful to just have your infantry in shield wall and hold fire until enemies are close enough. Archers are best behind them and on a hill whenever possible. If you have horse archers place them to the left side of your shield wall to shoot at charging infantry at their weapon hand. Your cav is best used as clean up or to draw attention to expose the weapon hand of enemy infantry to archers. Depending on the situation you may choose to order your horse archers to follow their sergeants because it is the only significant AI improvement from Warband.
With careful timing and repositioning, you can **** on the AI. I set my battle size to 1000 and the most I have been able to kill 1000 troops at best.
