Tested things out for a while.
Let me preface this whole thing: I'm not saying that the Gravis/Lorica should be buffed. I just want its damage output to be primarily bounded by how well I can aim and lead, not by spread RNG. Using a weapon with horrible spread feels terrible compared with an accurate weapon with equivalent effective DPS. If the devs intended for the Gravis/Lorica to do less damage at particular ranges, there's absolutely nothing wrong with that, but please strongly consider shrinking the spread to pre-patch levels and using the damage curve to do this.
This is the approximate spread of the T4 Lorica at max range. The wall is ~4.8k away, measured against allied ship distance indicators. The least accurate shots will land just short of the blue portion of the crosshair ticks. The light artillery destroyer to the upper right is ~4.1k away at this moment; compare with size of spread circle.
Now let's look at the spread for the T4 Morningstar, which I assume has the same weapon as the T4 Voronezh:
At this distance not a single projectile missed the enemy. The spread of the heavy plasma cannons at 5k comfortably fits inside the small circle on your crosshair graphic, as the yellow spread ticks approximately indicate.
Here's a live example.
Let's do some quick-and-dirty estimates by counting pixels...
I'm firing at a not-Monarch, I think, which is the largest target in the game seen from the side, next to the not-Zmey. I'm not firing at the center of his ship in this screenshot, but for example's sake let's move the circle a bit. The circle is radius 42px, area ~5542px. I'm probably overestimating the spread in this picture, so let's say really generously that the spread is radius 35px, area ~3848px. The green box covers 80x23px, area 1840px.
The spread is biased towards the center, but even being generous with the spread, firing at the largest target available in most situations at 4.4k, I can expect only about half of my projectiles to hit? This more or less matches up with in-game experience, by the way - at that range there are sometimes volleys where zero projectiles hit.
And if we're looking at a smaller ship like an artillery cruiser from the front, you might hit 15% of your shots with the light plasma cannon even with optimal aim vs. a stationary target. And in this situation you do pretty much the same damage whether they're evading or not, so they might as well sit still and shoot back. You might have a hard time hitting an artillery cruiser that's trying to evade with heavy plasma, but if you're good enough I bet you can do better than the spread on the light plasma allows you to.
I don't have any idea what the Jutland/Monarch's guns shoot like, so I checked some old videos. This is from https://youtu.be/r4eQMel_Gvs?t=4m58s:
Bounding circle is, again, just smaller than the spread indicator. He's hitting most of his shots at 4.4k against a Grenada, which at this angle is similar to a Zmey from the side. I assume this hasn't changed too much - someone who has the Trident or Jutland, let me know if I'm really off. The heavy ballistic cannons also have pretty good projectile speed, and has the additional advantage of withering firepower at close range.
E: Turns out I was totally lying about all the DPS stuff. I still can't tell for sure whether the damage listed on the stats spreadsheet is for the full volley or for individual projectiles, because the Jutland looks pretty off.
If nothing else, devs, please at least tell me whether it's a conscious decision. I'd much rather have lower damage and more accuracy for the same effective DPS.