It's not only a loot issue. It's a game / class / mechanics design issue that's been ongoing for years in wow, and will most likely keep going on, at least in some measure, hopefully not in the same scale than what we've been seeing in Legion, and removing ML means removing the only tool we had at our disposal to remedy to this design issue.
I don't think PL only will make fixing this more of a priority. Quick example : arcano and Aman'thul are still BiS trinkets by a huge margin for a few (a lot ? didn't stay up to date on all specs) specs in the game, and they're PL only, and still one of the most egregious cases of "1 drop makes your dps broken" I have seen in the game yet.