Unfortunately without a bigger pool of loot tables to draw from it can't be determined properly. At times it can feel like RNG screws you everytime and rewards the other people that didn't do crap. Sadly that is the burden of RNG systems. Personally wish they'd just give us exotics that had chances to roll different perks, this would cause people to keep farming for that perfect exotic. But instead they made every Ghorn and icebreaker the exact same and that's all we see at higher levels in PvE.