At T2 other than maybe the Aeon destroyer -because its torp.defense- no ship should be able to survive 1 on 1 vs. a dedicated antinavy vessel (submarine, torp.boat) of same tech level, not to mention come out victorious.
Right now even though, for example, the Cybrans have a dedicated T2 antinavy submarine, it's still better to make a destroyer to counter stuff in the water.

The Seraphim T3 sub. should be the best just under the the Aeon Tempest and T3 torp.bomber, and maybe the UEF Atlantis. Non-damage wise only the UEF torp.boat should be the better one because of its insane torp. defense. But just by antinavy -torpedo /depth charge projectile- damage wise everything else should be weaker.
It was not long ago, there was a match where one player lost a fleet of T2 subs to frigates and destroyers. That should have never happened. Antinavy assets should always be superior to everything else in the water during 1 on 1 same tier naval combat.

All in all, dedicated antinavy should be the bane of all in the water across all tier levels.
I suggest to either buff torpedo and depth charge damage or

As of now, producing submarines quickly becomes useless as soon as the opponent has more than a couple of frigates or just a few destroyers.