this is a single player game with command console i'm sure if you wanted to even the score you can spawn instantly 600 tier 6 troops into your army or w/e the hell you want. there are mods that can tweek exp for troops also
personally i'm glad they are getting free troops and free exp so i have something to fight. there are people that send troop on every encounter and execute every lord so they don't have to do the fighting, and there are people that don't lol. i'm currently using a mod that makes lord armies stronger so i have more of a challenge fighting higher tier troops. also modding to boost army and battle sizes so i'm fighting avg 1000 men armies instead of 500 men armies, also boosted bandit and looter party sizes. i've read a post of people complaining they are too big in vanilla... lol people are different.