so, a number of interesting ideas here. let me address them paragraph by paragraph.
firstly, you say right here
Okay, I really don't want to strawman you so let me first verify your point. I see here "The issue isnt that people will be jerks to DPS" followed immediately by "people are already jerks to tanks and healers, why should DPS get a pass". I believe I might be misunderstanding you so I would ask you to elaborate.
I find from my personal experience with XIV that I don't need to see a number in this game to know I'm under performing. In fact, I would argue that the stringent nature of the DPS checks kind of makes it apparent with no uncertain terms. I understand that my experience is very personal and may not be reflective of the average player. If you are regularly clearing a dungeon but you show up once and the DPS checks aren't getting passed then you can be largely certain its that Dragoon you were referring to. If all of your dungeons are clearing really slow then you can be certain it's your own doing. As far as this Bard is concerned, that particular binary--- whether the checks are getting passed regularly--- is the only important part of the readout and you don't need a 3rd party posting leaderboards after every single trash pull, which, I am sad to say, happens in about 10% (speculative, not calculated) of my solo WoW PUGs.
At the risk of sounding like a no good hippie lib, I think commendations should be handed to the players that take an active interest in the community, not the ones pumping out big numbers. I speculate adding a commendation that can only go to DPS would help promote this philosophy.
I remind all this is a socially-aspected game, not a spreadsheet simulator.
While little peer reviewed research has been done on how this affects video games, there are a plethora of studies concerning the comparative effects of positive and negative reinforcement in relation to behavioral modification. For your perusal I have placed links here and here, along with a hilarious short comic on why buisinesses hate yelp here simply because I think this comic explains perfectly why giving people the unfettered means to complain about each other is a universally bad thing.