Sergeant at Arms
That's one way for factions to get snowballed. Wait 7 days to respawn. Wait another 3-4 days to recruit enough troops to dare venture out to recruit more or they are gonna get eaten by bandits. By the time they have recruited enough troops it has been 3 ingame weeks and the enemy has taken half their fiefs. 10% is nothing, it is about 10-15 troops on average.not only that, 10% snowballs them, they can run around recruiting like crazy - once there is a critical mass of troops, they don't deal with bandits, only other NPC enemies / player. Starting from 0 delays that process. I don't think its hard to put a rule in that says NPC defeated = stay in own fief until recruit X then resume normal behavior.
Do that, or 10% and they stay in their fief for 7 days or whatever (I think that is worse tho).
Maybe a better solution is after a defeat, they 'disappear' for 7 days and then spawn with their 10% - I feel like that's what used to happen in warband, although I cant remember.