Normal damage, good AI (not that it seems to matter).
I've not once fought against Black Khergit raiders since they stuck me full of arrows and stole my first hunter! Grr! I run away and hide in a town for a night, and they usually go away.
I have two levels of Pathfinding, no companions and a Charger, and I don't have any troubles running away from just about anything, whether I am loaded with trading cargo or not.
If you're slow and you're chased by Black Khergit raiders or Dark Hunters, just release all prisoners, disband your slowest men, drop your cargo of smoked fish and head for the nearest town. Once you get there, you're safe.