I haven't tried tanking in this game yet. That said, I have tanked in other MMOs. In WoW I've main tanked several at least half of the Burning Crusade dungeons as a death knight. I was well aware of what my limits were and what tools I had to hold aggro. And a few times I was tanking for a group that effectively didn't have a healer due to the 'healer' only doing dps. In those instances my limited self healing was the only healing I had access to, thus I'd be unable to handle as large of groups as usual. So naturally I got booted a time or two when the not-actually-a-healer was team leader and thought I was being too cautious in my pulls.
In City of Heroes (anyone else remember it?) one of my many characters was an Ice Armor/Warmace tanker. And I was good at holding aggro. For those who never played it, an Ice Armor tanker was Defense to damage type based rather then Resistance to damage type based. And until around level 18 they had little to no defense to fire and energy attacks. Meaning that if the group is facing things doing fire and/or energy damage I was basically a squishy with extra hit points and all the aggro. Speaking of aggro, a couple months after I started playing City of Heroes the devs put a cap on how much aggro anyone could have at a time. That cap was 16. If the group's tank already had 16 enemies aggroed onto them, they absolutely couldn't pull any more. For every additional add the tanker tries to tank, one of the previous 16 mobs they were tanking would peal off to attack someone else. You wouldn't believe the amount of vitriol I got at times for daring to not pull entire rooms. Rooms that had anywhere from 30 to 150 enemies in them. Remember, aggro cap of 16. Even if I wanted to try holding that much aggro, and could survive doing so, I couldn't manage it due to game mechanics saying I couldn't.
That said, "you pull it you tank it" seems like a toxic attitude to me. And that's coming from someone who considers it a point of pride to be capable of handling any aggro they manage to pull. Hell, I've managed to main tank with support classes in various MMOs. And in DDO I've managed to off-tank on a sorcerer.