Raider artillery keeps shooting random walls, even if there are no guard towers or other strategic targets within those walls.
When the new raider units came out, i was shocked to find the catapult blasting my defensive towers into dust in a few shots, while staying out of range. After that, I’ve prioritised destroying catapults and battering rams as soon as they show up.
What really helps me, is that the rest of the army just runs off and leaves the artillery unguarded. They show up together, but the catapults and battering rams get stuck on the outskirts of town, shooting at towers and walls, while the rest of the army runs ahead into the shooting alleys of the village to get mowed down by guardtowers, while my horse runs around and takes out the artillery.