It dawned on me that a lot of people don't know they are bad. I made another thread about how they should include a self parser within the game but that would still depend on people using it.
So here is an additional idea - make some 4 man content (maybe the next expert dungeon?) that splits the 2 DPS away from the party. They then have 60 seconds to bring down what amounts to a target dummy. Failure to do so kills them and then additional monsters spawn with the party and the DPS is dead on the ground.
Now players would instantly realize if they in fact are bad at their job. Healers and Tanks already have mechanics that show them if they are bad. (Aggro is lost, someone dies). But DPS doesn't really because there are two DPS to the party.
The purpose isn't to deride people but the FIRST step to improvement is acknowledging what you are currently doing is sub par.