I think people have lost sight of a very important issue.
Who wants to be anywhere near a warp core carrying hull with 1500 quantum torpedo warheads when it blows up? They'll have to invent a new word for 'collateral'
And that's before the stardrive section even begins to kerplode.
What makes you think quantum or photon torpedo warheads even have the abilty to "cook off" (prematurely detonate due to external damage).
And if those warheads were vulnerable to cooking off, I doubt it would matter much whether it was 20 torpedos blowing up or 2000. The results would be pretty much the same to the ship in question.