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

[AlereRaeder]

Are we talking DF groups here? Would kicking people for low dps even be allowed in DF groups?

Nope that would mean they'd be violating the rules of Vote Dismiss. If you were to be spontaneously kicked by a group of 3 who never spoke a word you could file a report and get those 3 players banned(idk how long) GMs can check everything from chat log to player positions, HP, and damage done to them at given times.
Party Finders on the other hand are a more little touchy and someone can't just roll up in your PF and expect to be given a chance by every leader, that leader might have heard about you and kick you if wants. PF rules are mostly made by the leader, if Party Finder entry comment says Slaying ring is locked for him and you take it; he can file a report and you can get banned( like personally by a GM). This is why lootmaster is coming. Moreover, if he explicitly says the reason why he kicked you is low dps parsing then he can get banned. Mostly harassment SE doesn't want to see.