As a rule I only use salvoes against battleships and carriers. I find that a 2-torpedo spread against battleships, with the spread angle set to pop the eels into the fore and aft magazines, gives the best results.
Against carriers ... well, my evasion tactics aren't the best and generally I want to shoot as many torpedoes as needed in as little time as possible so I can get away quick. I've only fired a 3-shot salvo once, and that was when I found a Bogue class escorted by half a dozen Clemsons ... on 4th July.
