So I want to start off by saying I'm very happy with the weapon balance right now. So many weapons that seemed doomed to a mediocre existence now have distinct, valuable niches. A good example of this is the gallery of small kinteic weapons: railguns, needlers, autocannons, and dual autocannons. With this many weapons competing in the same slot with the same damage type it feels like some of them should turn out useless, but I find myself considering the qualities of each weapon carefully and picking out every one of these options for different ships.
Recent patches have extended this to a lot of weapons like the hephaestus, storm needler, heavy autocannon, phase lance, graviton, and none of these directly outshine any of the options I was using before. Except the hellbore. It still has a niche, being cheaper and having lower flux/second than the hephaestus, but that niche got a lot smaller. The difference in performance is massive, so if you can sacrifice somewhere else to make the upgrade, you will, and most of the time, you can.
Before talking about how it could get buffed, let me lay out how it shouldn't get buffed: accuracy and speed. The hephaestus is meant to be a better generalist providing good armor and hull damage against all targets, while the hellbore is meant to be atrocious against smaller targets but very effective against larger ones. Buffing the accuracy would serve make it more like the hephaestus which is not what we want to do here even if it would make it more effective.
As for how it should get buffed, I think the hellbore needs to do more hull damage. I forget who pointed it out, but someone mentioned that even against larger ships the hephy massively outperforms the hellbore because you spend a lot more time shooting hull than armor, and while the hellbore is impressive against heavy armor its damage against hull is a bit underwhelming for such a slow and inaccurate weapon. What I'd like to see is maybe an extra 750 fragmentation damage added on top of its existing damage, plus some extra flux cost to go along with it. Maybe bump up the flux/shot up to 1000. I'd prefer this over increasing the explosive damage because that would make its anti-armor capabilities too good; at present some armor setups can tank multiple hellbore shots in the same spot before being stripped. I don't think it needs any help against armor, but its effectiveness against hull leaves much to be desired. And if I do somehow hit a frigate's hull with one of these, I don't think it's too much to ask for it to pop in one shot.