Same drop rate as any other exotic gun in the game. The reason it's "rare" is because it's the most wanted gun in the game. So you'll see more people complaining about it. Remember red death before xur sold it 2 months ago? No one mentioned it until crota hard mode. As soon as hard mode was released Everyone considered it just as rare as Gjallarhorn even though xur sold it twice before ctota dlc. It's all in your guy's head.