This is part of the problem - every raiding tank knows that they are expected on launch day to know the fine details and a good strategy of every fight in the instance, and that if they make a mistake and die then they're awful but if a dps or healer does it then it counts as a learning curve and a mistake. People expect the tank to do everything and whilst most of the tanks who've been doing it for years and are established have and can do this easily and have no problems taking a leadership and tactical role; people coming into it new who then get people that expect that from a tank and then get arsey when they can't deliver the whole package, is extraordinarily offputting. The expectation is not fair and does not reflect reality.
Back at Cata start I had that. I've been since BC and know what I'm doing. I'd been bear tanking in WOTLK too. Dinged, started a heroic dungeon with the guild. This was when Swipe and Thrash had a shared CD and bears were going mad and getting AOE aggro was nigh on impossible if the dps outgeared you and didn't use threat drops. I had a mage in the guild who was just treating it like a WOTLK heroic and getting upset at how holding aggro was a nightmare, kept dieing and then became patronising. The tank doesn't need to be in control of the group but he does need to be in control of the enemies, and when that was more difficult, getting dps berating you who did nothing to help themselves almost made me quit bear tanking.
It's so demoralizing and you don't realise until you're actually struggling yourself