It's normal for a navy player to make their own torpedo planes and just trust that the air player will provide cover with ASFs when necessary. It's normal to get T2 air before T2 navy so you can make engineers and a T2 pgen.
For a lot of situations, even if the torps only get 1 pass, they might do enough damage to be worthwhile, especially against subs, which tend to have not a lot of HP for their price.
- torpedo planes cost 270 mass each (the unit DB says 240 for some reason, but it's wrong)
- You can kill a T1 sub in 1 pass, and the subs cost more than 1 torpedo plane
- a T2 sub takes 2-3 passes (2 for Cybran, 3 for Aeon) but they cost more than 4 torps
- a T3 sub takes 6 passes but they cost more than 11 torps
Even if half your torps get shot down before they drop anything, that can be cost-efficient against T3 subs.
You can ground-fire with destroyers. Aeon destroyers especially have a nice AOE that can work. Aeon destroyers also have stronger torpedoes than other factions which makes them dangerous to subs.
Ground-fire with battleships is even better, because they have even bigger AOE.