The problem is thorn is both not OP and very OP at the same time. Hand cannons in general need a range nerf, but if thorn was used anywhere between shotgun-fusion-auto range I'd say it would be pretty balanced, however you can use it well beyond those ranges, which is what makes it OP. The best thing to do would be to hit hand cannons with a general range nerf, and then remove send it from thorn in exchange for something else like skip rounds.