It seems that with the newer MOP dungeons being easier than the ones in early Cata, there have been fewer pugs that end up wiping and unable to finish a dungeon.
But that being said, there have been some pretty unpleasant runs, and also in LFR. To be honest, I wish that there was a rule that said tanks cannot queue for LFR unless they pass the character audit. That way, they would at least have to take the time to research and understand what gear, stats (because they would have to purchase gems), enchants, and reforges are proper for their class.
It would lead to a bit less pain in LFR and perhaps would waive the need for things like a 5% buff (which at time of this writing, Blizzard will be implementing with the next patch).