the single-shot kills against Borg cubes in Voyager's "Endgame" episode do what it took 4 Q-torps to do to a single significantly-smaller sphere in "First Contact".
To be fair, I'm not sure 4 torpedoes were really necessary in FC. I can see Our Heroes figuring that overkill was the best option, especially against an enemy that's shown an ability to quickly adapt to weapons systems.