It's a unique gun that every player gets the chance to earn. It doesn't come from the lighthouse, it doesn't come from Hard Crota or VoG, it isn't sold by Xur, it's a missive. Run enough bounties and you'll get the chance to earn one. Nerf it and what happens? Another gun takes it place. Then everyone will want that nerfed, and then the next, and so on. Unnerf autorifles is my answer, but then everyone will complain about Suros again.