I do think that submarines are not a good addition to the game. Not that it matters because they are in and they wouldn’t be removed even if every single player complained about then.
Having said that, after playing on the test server quite a lot, here are my thoughts about subs:
1) there shouldn’t be more than one sub per team. Two is just awful, while three…. no, 1 sub/team is more than enough.
2) the homing torpedoes, as others pointed out already, are just broken. Unless you go straight towards the sub, there’s no way to avoid the torpedoes, which turn too fast.
3) they are more difficult to kill. I hit one with 3 depth charges, it just kept going with lots health left.
4) generally speaking I find submarines very distracting. Same thing happened to me in World of Tanks when WG felt the overwhelming impulse to add wheeled vehicles to the game, which is now unplayable, just speed and extreme repetiveness.
As I said: 1 sub per team is ok, I guess.