I believe there has to be a % drop rate of each item in the game. How else would explain that certain weapons like gally are rarer than other weapons like no land beyond. I look at it like a slot machine...take a hat and throw in every item in the game once. Then take that same hat and throw in all the items that you want to be less rare multiple more times. Now we have 1 Ghorn and 5 no land beyonce in that hat. Mixup the hat and pick one out randomly... Destinys RNG?!? Who knows...who knows how random it really is?!