Not necessarily. It could be predetermined what loot you wish to roll for. The groups I have run with all pretty much agree that you either roll on the loot for the role you're currently playing, or a different role you would prefer but didn't play as for that run. However, freedom to roll for multiple roles is usually considered unfair.
So, that should solve the problem you have with the idea.
This. Also, there's the chance for accidentally clicking the wrong button. Kind of a mouth-breather's mistake, but it does happen. The master looter could also make a similar mistake, but you have potential for multiple "accidents" vs one, so chances are reduced with a master loot system.
Also, it's possible the group leader could screw over the group, so it's best not to run with strangers who are using master loot. Master Loot should also be limited to preformed groups, and not an option for Duty Finder groups.
There is no perfect looting system, but this would be a nice option for honest groups.
