Those are the baseline facts (except its type I and type IV - Type ones did less damage but you can fit more and were easier to kill, type IVs were larger so they did more damage, were harder to kill, but you could fit less in your ammo stores).
A battleship could take out a heavy cruiser in one salvo if the heavy cruiser was an idiot, lol.
Thats not to say that the battleship would end up knocking the crap out of the heavy cruiser, but it probably wouldn't be the drones that did it - and definately not in one salvo.
If i were in a heavy cruiser up against a battleship - I would run, but if i couldn't do that and I had to fight it, I would run at medium-high speed with ECM up - ECM disrupts the accuracy of photon torpedoes pretty badly. I'd turn into it and fire my torps at any opportunity I could, and depending on current circumstance, use my heavier phasers, too.
If he were dumb, he'd launch all his drones at me all at once. I could beam out a mine into space between me and the drone wave - the drones set off the mine, causing the drones to be destroyed - poor mans point defense.
If he were smart, he would actually charge at me, just barely over the speed of the drones he was firing, and fire the drones once at a time on my way in. This way, all the drones start off spread out (so they can't be mined like above) but they do end up coming in closer to one another when they come in, saturating point defense.
Drones are very lethal against people who don't know what to do against them. Drones are very easy to take care of once you've figured out how, in most circumstances.
Another tactic was to grab someone with a tractor beam and then unload all your drones on him (the tractor prevents him from running, and prevents him from launching a decoy).