In a 1 on 1 encounter no dedicated moble antinavy asset should take so much effort, not to mention loose, against another unit of the same tier as it takes now. Prime example is at T1 a UEF underwater submarine vs. a UEF frigate in its vision range. Such an encounter should end in just a few seconds (but no ore than 5) with the sinking of the frigate.
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 -which might be better- make everything that can be targeted by antinavy weapons/projectiles to be much more susceptible to torpedo, depth charge and other such antinavy damage.
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.