I think Heph is good right now, wouldn't use a Hellbore over it on any ship in the base game.
L ballistic slots are very good and aren't that plentiful, feels much better to put high impact weapons in them.
An example fight for Hellbore's best case (1000 FP Hegemony fleet filled with huge/slow armor bricks):
The sequence at
3:45 shows off Hellbore's weak point very well:
Shoots fighter, shoots fighter, misses Onslaught, misses Onslaught, hits Onslaught, shoots between Onslaught and Grendel. 6 shots, 1 meaningful hit (ok, only had a good target for 5)
Even when it hits: spread is generally big enough to damage armor in various places without doing hull damage, Heph just drills the same general area and eats up both armor and hull.
For those who don't want to watch a video, it's 3 Executors with 1 Hellbore and 1 Heph Manticore escorting each one, mostly left to their own devices after clicking the top border.
Hellbore loadout and combat results, Hellbore manticores are the ones in the blue rectangles (scrolling over them at the end of the video):
In general Heph does much more than the Hellbore against any fleet for me.
Ofc it should do more for 190 extra flux, IMO op is close to even since advanced gyros are basically mandatory for Hellbore.
I said it before and I'll say it again: the problem with HAG is not the stats of the weapon itself, it's that the weapon type - large explosive ballistic - has almost no practical use when all the strongest enemies in the game are (very) high tech ships.
It has a very practical use, in my experience: not letting Remnants get away with minimal hull damage.
Against low-armor high-shield ships it's important that you actually kill them once the shield pops, otherwise you spent all that time shooting it for basically nothing.
This was addressed last time you brought it up, piling on to the 2 previous posters: going heavy on HE/autolance/high hit strength energy against remnants is very good.
Radiant has the same hull as Onslaught with armor that's pretty close, no HA but it's guaranteed impact mitigation+damage control+polarized armor. Every time you let it jump away you have to go through the full base 0.6 shields again.
Apex is very durable for a cruiser with guaranteed impact mitigation+damage control, whenever it escapes it regenerates both shields and some hull (elite CE).
Nova is basically begging for HE to be spammed into the sides.
Since the only good HE options for ballistic are mauler or L the L HEs are good by default, S or M can take care of kinetic (you really don't need as much kinetic as you think).