Actually they are... If I kill something in the wild in say, World of Warcraft, I'm unsure what the loot will be. I have an idea sure, but so does Destiny. Then you look at WoW's dungeons and raids, this has defined drops you're just subject to the RNG of them actually dropping. This works exactly the same in Destiny. If you want Fatebringer you know exactly the boss you should kill, even in this RNG loot system.