I think a good approach to a dps meter would be a grading system, like Devil May Cry's Style Meter.
The more PPS you do the more it fills, the more it fills the higher the grade. You set up 1 meter per dungeon pull and boss. Why PPS? Because that way overgearing doesn't give you more rewards, you have to achieve the Potency per second dished, not the damage.
Like dungeons are right now, we have: 2 massive pulls, 1 boss, 2 massive pulls, 1 boss, 2 massive pulls and 1 boss. With some variations with smaller pulls before certain bosses but you get the idea. We would get 1 grading per massive pull and 1 grading per boss, ending the dungeon with 6 pull Ranks and 3 boss ranks. At the end we would get an average and that's our final Rank.
Make it an overlay like the Job Gauges so you can't copypaste your "dps" in the chat and there should be no harassment. Give extra tomestones and System Based Commendations as rewards based on on Rank Achieved; B rank gives you 10 extra tomes and a Silver Commendation, A gives you 25 extra tomes and a Gold Commendation, and S gives you 50 extra tomes and a Platinum Commendation.
Why tomestones? Rewarding efficient play with less grind. Why system commendations? Because most players if a dungeons goes quick will commend the "aoe dps class", meaning that maybe there was a melee that was destroying a smn in aoe situations and they go uncommended because the party assumed the smn was the one doing the awesome aoe damage. Or just tanks and healers, because they are the "most valuable" party members.
For extra flair you can have each Job Teacher or relevant character commend you via linkshell call after a pull is done. Say you are running dragoon and you hit a "bad" rank (C or less), Alberic would chime in to support you and cheer you to do better; something like "Come on [Character Name], I know you can do better, you are the Azure Dragoon after all!!". If you reach one of the rank with rewards, Estinien would condescendingly praise you, like he always does xP
Put a mount or something with the new commendation system and there's your incentive for people to get better. This way you've got a personal "DPS" meter, a Ranking towards other players that doesn't depend on other players commending you and extra rewards for doing good, both in the form of a mount/glam and extra tomestones per dungeon run.