The last 2 points make this thing really very good in this specific war (surveillance assets can do whatever they want and russian captains seemed very complacent), but very inefficient anytime else. Also I'd say you should be able to easily adapt something like the various CIWSs (which currently have ancient designs...) to this threat. Also: once you notice the threat (which 2/3 last incident did?), why not level the playing field for your (hopefully not all drunken...) sailors and just flare up the whole environment (which should have helped here: https://www.youtube.com/watch?v=RwXzaBixvL8 - also I don't really agree with this guy, that more ships help in defending against a swarming attack when they don't know how to kill the swarm...)