DPS display could easily be solved with a system already in game.

[Ghasto]

He can think that, but he just needs to come out and say it.

I did say it, any party leader is well within their right to remove a player that is not playing to their standard.
In the case of healers and tanks it's obvious, with DPS it is not, this is where parsing comes into play.
Why don't you petition SE to also remove the party list from showing to anyone but the healers so nobody knows that they're not healing? or hide the enmity list from anyone who is not a tank?