Again, it is not set on one specific faction all the time. It depends on a multitude of things, but in the end it come downs too RNG. This issue has somewhat gotten better since this thread was started. Still not fully fixed though.
But I commend you for trying to keep this thread alive.
Its rng if its a bit of land, not 4 towns + many castles. Keep in mind this is a pretty fresh save as well from 2 days ago(day ~180). I noticed khuzaits being "op" in previous saves as well as some other factions, but those other factions dont seem op now(battania). Outside of the Khuzaits only the southern empire seems maybe tad bit too strong(would have to test them more to be sure).
Multiple times i saw a faction(khuzait mostly, but other factions as well) to take a town then sue for peace before the losing faction even retaliated..seems quite unrealistic from the losing side. Unless they face utter defeat or were super weak, which wasn't the case. So factions that took the town basically got away with dealing a cheap shot then avoiding their vulnerable state when they could easily lose the town with a peace treaty. Quite unrealistic and game breaking.