You cannot know the weighted constraints modifying the RNG. The game changes constantly and the chance that the constraints change is also in flux. Assumption 1: this is not a generic RNG Assumption 2: Those values can be manipulated based on the current content. i.e. you could not get the Dragon's Breath before The Dark Below. Now we have it, so there is a possibility that it has a better chance to appear. Think D&D loot tables with the rare stuff on 1 and 100 roles.