Ninjalooting is a community problem, not a game mechanics problem. Trying to address it by changing mechanics will not solve the problem, but will create new ones.
As much as i hate to say it : THIS
Ninjalooting can never be entirely removed since there are so many different opinions of what it is.
The community can not be held responsible by simply using what the game let them legally do. There will always be players that use what tools are given, and right now the lootsystem gives them option to take whatever they want regardless of actual need.
Name what problems that will come from improving/changing the loot mecanics?
If you simply remove the option to take all items in the entire game with a needroll and let those that can actually benefit from the item you help alot of players and removes alot of problems and frustration. The only ones that could possible be against a system where items are given priority to those that use them are the ninjalooters themselves.
But then again, prove me wrong by stating the new problems that will occur?
Players whine about not earning cash fast enough because they like to sell every boss item in the game?
Players whine about not able to gear up all their companions that they dont use anyway?
Let us know what new problems that might occur by using a common sense lootsystem in a constructive way