The biggest problem when using such missile waves, is that all the missiles will home on one ship, the first they find, and ignore the rest. If the ship was not alone, worst case it being a neutral you hit, or against a CVBG or similar it means you create a small hole in their defenses. I repeat: small, compared to the cost.
Firing them at slightly different bearings might get you better results, but not all that often. If you could just waypoint them...
Against AI, you usually have more luck firing an active torpedo and enabling it very very early. I've had five kills per weapon slot that way. And that seems to be with collision avoidance scripts, and what should be plenty of space inside the formation.