Oh, fine then.
Right now I'm trying bombardment, I started with carronades because they deal the most raw damage, I put 90HS of carronades into a design and then spawned it. It had the same rough 10% hit chance, killing about 0-1 units per round. Then I changed this to 30x4 Railguns, this worked very well, and that single ship could now reliably kill around 8 units every round. Still not a lot, though. I'll try even smaller weapons.