Just because it was a PVE perk doesn't mean it couldn't do damage in PVP. No one complained about Reservoir Burst, but it still got not 1, but 3 nerfs (larger mag, damage, and archetype). Onslaught got nerfed to scale damage with ROF during a meta where ARs were worthless in and out of PVE. Master of Arms was intended to be a PVP perk, but dominated PVE. It didn't really dominate PVP either until Luna/ NF were nerfed into oblivion (and nerfed harder than they said too). Desperado was a PVP perk, but was somehow too powerful in PVE even though almost no one used it there. They never said they were nerfing Magnificent Howl's damage, only where it was applied and for how many shots. Body shots according to how they worded the nerf are still supposed to do over 150% more damage with the buff. Then they bring in Hawkmoon which could be compared to it, but with extra steps and impact not matching the archetype (has the impact of a 180, but performs like a 140). Everyone complained about how bad Oxygen was, but Bungie never did anything, and it won't be good unless Meganeura is buffed to be on par with Energy Accelerant. There's more I'm sure.

The difference is negligible, but rockets only get 7 or 8 shots I think, so Vorpal instantly exceeds that damage after the 6th shot.