The idea for games like this is to loot in a difficulty until it becomes too easy and move on to the next until you are at the hardest content. Take away that few exotics and only 3 or 4 named items are actually useful for a second and look at the 3/5/7% model for missions currently. The percentage differences are not nearly enough of an incentive to build strategies to farm less forgiving missions. I think you could continue to have total RNG on pieces but up the drop rates for exotics and named to 3/6/10% or keep the drop rates but embed higher floors for attributes based on level to something like Hard 0%, Challenging 25%, Heroic 50%. I think the latter would be better because it would strongly incentivize the hardest content and the player base building skills and gear to complete it.