Heroics are such a joke, especially if you have one overgeared DPS in your group, do you really care that much if a DPS in greens/blues is doing low DPS? Or do you really love to ruin the enjoyment of the game for others, no matter the reason? Or by "abysmal", do you mean something like 10k?
I could understand waiting and kicking someone if his low DPS makes a heroic more difficult, almost impossible to complete, but that's not the case with MoP.
If I know I won't be able to do 7 heroic scenarios in a week I sometimes do normal scenarios for some quick valor infusion to help me cap. However, normal scenarios are no longer place for good players and are populated by fresh 90s.
You would not believe the dps they do. It's beneath abysmal. I once had an absolutely terrible group in Brewmoon Festival. I always assume that others will go for the vermin first so I jump straight to saurok to stealth past trash and quickly dispatch him. I've done just that, he is at about 10%, I look behind and I see them swimming dazed with every single mob on them.
I move on, to water elemental. I'm nearly killing it when they catch up. And lo and behold, they put pet to tank the boss, it gets the shield and I have to wait 15 seconds for it to run out because it's hard to disable pet taunts.
That item to help you? Derpa Derpa. And they put all the traps they can right in the middle of the village.
And all through this, hunter was doing steady 15k dps while warlock trudged along with 10k dps. Horrific. It took forever to complete even if I was nearly soloing it.
Hell, I sometimes solo some of the scenarios (Crypt of the Forgotten Kings! It must be weird to them when they are killing these vortexes and suddenly bam, scenario completed gl hf bb) and it proves to be quicker than waiting for them to catch up and more fun.