We should be focussing on both parts of a pvp experience--the original player and the player he or she is playing against.
While I have not played a submarine, I can imagine why people find it fun. Hence why people still continue to play submarines. Being on the receiving end as a battleship, however, is not an enjoyable experience.
There's a lack of interaction between the two classes. Ideally, the submarine should sneak into range without the battleship being aware and launch its alpha strike from a position and range the battleship can not evade. I can imagine that requires some patience and timing. Great, for the submarine.
As a battleship player, though, there's not terribly much we can do as indviduals. In short, submarine attacks feel arbitrary and not much fun. It's more like something you endure--like a bad internet connection randomly dropping you once every 6 games.
Is this a balance question? Are subs OP? Are battleships UP? No, it isn't. This is about fun. And right now it's not fun to play against submarines as a battleship. We should try to figure out a way for battleships to play against submarines and submarines to play against battleships and both groups of players enjoy the experience.
Because right now, it's not fun for me. I don't want to win every time, or even most of the time, but I want some some more interaction between us.
(Note, yes, I am aware there's supposed to be some rock paper scissors going on, but let's not kid ourselves and believe this is happening in the current game. Plus it's tilted a little bit too far, I think. People should have some advantages, but I think the advantage of paper over rock is a bit overwhelming. Skill should also come into play, not simply the RPS class system.)