Graviton Hellbores have no use. They do about half the damage of APBs, and have the same range.
Emmisive Armor is easily countered by mounts. A large mount PPB V does 120-100 dmg. That can breach Emmissive Armor in a single shot.
As such, Torpedoes, like Graviton Hellbores, are pretty useless.
The key to APBs is that you don't research them in the early-mid game. Use DUCs, then PPBs, then APBs + Shield Depleters (not Disruptors).
