Faction leader doesn't notice ambushing army, quickly swarm them with nothing but melee troops and voila, immediate way to confederate whole regions only having to beat one army. Then declare war on a faction to lure the enemy faction leader away from its garrison (I could only afford 1 stack which couldn't really beat a garrison+full stack). What I did was park an army in the woods in ambush mode. The confederation mechanic is nice, but a bit exploit-y. But overall their army is a blast to play with, although mammoths beat everything so far, amazing unit, but have to limit myself on them.
So all Norsca settlement battles are just open map ones, which makes me consider all settlements a write-off when attacked by a full stack with slightly above average enemy troops. On the Norsca playthrough itself, their infantry is really meant to be a glass cannon, which makes garrisons a bit on the weak side seeing as how Norsca doesn't have walls. So sadly I gave up on that campaign, now have to wait for CA to patch it.
This locked me out of all of them, which has apparently affected more people. Norsca was fun to play for a bit, but my monster hunt quest bugged out and aborted itself on the first objective.