It looks like Small, Fast torpedos that are mass-driven about 10km out (cold), then quickly go hot and home towards the enemy ship, are the weapon of choice in ship to ship combat.
You can fire them at "I know the enemy's out there somewhere" range, and have the Torp's own sensors get a clearer view as it moves towards the faint smudge on the horizon.
The Torp only goes hot after 10km or so, or else the enemy vessel will know your exact location from the Torp's much greater temperature.
Such a torpedo might be able to home into the enemy ship from as far as a Light-hour away (or more), but can only be -targetted- when very close.
Of course, this lends itself to the idea of Counter-Torpedos, as the bright flare of the torpedo will be visible long before its cross-section is, meaning an anti-torp will be able to home in on the torp.
Beyond that, though, and you get into "we need little torpedos strapped to this big torpedo" territory that makes the warhead just not as cost effective as making the friggin' thing GO FASTER.