I would say that 90% of humanity are one enormous grab-asstic squad of hooting morons in any case. PUGs are bad because they're PUGs, not because people don't play their classes. You don't have to be able to play your class to not stand in fire or to realize that hitting a dude with a crazy bubble shield seems to hurt you back, or other EXTREMELY OBVIOUS mechanics that people ignore. This is because they're morons, not because they don't know their class. I'll hop into stuff on a healer (I am a terrible healer) and outperform PUG healers. This is because I'm not a colossal nitwit. I'm perfectly acceptable DPS and an actually good tank (server first Greenscale gloves, aw yis), but there is a lot of competence between 'most humans' and 'people who are actually good at games', with experience in a specific video game or with a specific class being a quick solve if your brains aren't made out of -blam!-in' pudding.