This is a funny topic.
I only raid with guilds as DPS, I've never not raided as dps outside of a stint in HC Dragon Soul progress when one of out healers left and we had no decent replacement.
But when I pug dungeons/raids, 90% of the time I tank or heal (when on non tanking hybrid, or on a hybrid that either has no tanking spec (shaman) or where tanking is the most boring thing in existence coughcoughMoPdruidcoughcough).
The only time I ever get blamed for something that is not my fault is when the off tank fucks up and someone says the general 'omg tanks have no clue' which is the same as when people 'healers suck' or 'dps sucks' even though you might be doing your part fine. All you have to do is tell them it wasn't your fuck up but the other guys and everything is gucci. I've never gotten shit after that.
I don't really see much difference tbh, when I interrupt or purge something as a tank, I would have done it as DPS or healer anyways. If you don't use your defensives to reduce the damage you take/not die even as DPS/healer you're pretty bad, it's not just a tanking thing. Positioning mobs isn't really a big deal (apart from that one time in was it wotlk or tbc where mobs were bugged and always tried to get behind you). It's not like anything needs marking outside of challenge mode these days (even then not really).
And it's like if say there's not enough interrupts on the brakenspore big add, people don't single out the tank for it, because that's not just you're responsibility/fuck up, but that of everyone that can interrupt (unless you're doing interrupting assignments or w/e.)
It basically boils down to don't be shit, no matter what spec you play, it's just that when you're shit as tank/healer it stands out more because you matter more.
I honestly pay more attention when I'm DPSing compared to tanking, but that's probably because I'm a meter whore who gets serious self esteem issues and gets all emo if I'm not at the top of the charts.