If you're already doing as much as you say you do, it's not about you. If dps is an issue on a run, the first fault lies on dps players and it seems your friends are not interested of the very basic, that is, keep gear up to date. I take it they just got to 60 if you've been running never reap and such. Going forward from that you reach dungeon where people had weeks to gear up from leveling gear, you simply can't run them in level 59 stuff.

As for their skill, I suspect one fault might be they have leveled in vacuum. I get it some people like to play in established groups but that also limits their view of how others play very drastically. If you really feel they need you as kick protection you should urge them to run df alone to get the grips. Yeah, they might get kicked, afterwards you ask them what expired and try to explain the reasons.