That gun is very hard to get (vault grinding takes long af), it is super strong in close combat and gets even more disgusting once it is charged up to 900 RPM without a damage reduction (you basically melt on sight when getting hit by it in charged mode in pvp). Players shouldn't be able to get a higher rate of fire on a gun just by dealing damage to an opponent. It should require kills to achieve such gun power. In PvE there are plenty of trash mobs and regular enemies, alongside with the infinite primary ammo change. A change to the perk function won't impact PvE on any crucial level while fixing a big problem with this gun in PvP. Make it happen, Bungie.