Yeah, the bandits are slightly rare. There should be a Raider landing (or of a similar name) along the coast of the Northernmost Fierdsvain city (closest to the Ravernstern) and along the same coast but to the south of the Westernsmost Ravenstern city (closest to the Fierdsvain). Sorry, I havent played the game in a while so i dont know the names of the cities off the top of my head

Alot of bandits on Ravenstern land that are easy to kill, id start there. Or the robbers on Sarleon land, there also easy to kill.

Try area between Marleons and river near Laria. Or Ravenstern land.

If you head up to Laria to find robbers, watch out for the occasional band Noldor elves, they're pretty quick, and OP as hell.