keen socket
Brigands, and certain other enemies, could be allowed to fight to the bitter end if escape is impossible without suffering attacks of opportunity. Overall I don't think there's anything wrong with fleeing and will to fight, but enemies who are pushed into a corner to die shouldn't always give up as easily as they do. It's a lot of fun for me when they are able to escape further into the dungeon, but less so when they are crawling to an obvious and literal dead end.
A fleeing enemy with all escape paths effectively blocked by opposing character's adjacency should still seek to stay out of the fight until their will to fight is replenished, but they could enter a state that allowed them to either counter melee attacks or take cover from ranged attacks and spells, or otherwise react to the situation more appropriately than becoming entirely passive, especially in case of other enemy types that have will to fight.
tawny yoke