Is this a common thing for tanks to do?

[Ashkendor]

Also, please do quote where I said or asked if all tanks are bad.

Your post is titled 'Is this a common thing for tanks to do?' immediately followed by:

Doing large pulls that is, and missing aoe aggro on some mobs.

Then you described a scenario with a tank that got hit by the vuln-up debuff as well. If you tank more often than you heal (as you stated you did), you already know the answer to the question you're asking. You are, in effect, asking rhetorically if bad tanks are common. My answer to that is: they aren't any more common than bad healers or bad dps. They're just more noticeable. I think what people are taking umbrage with is the fact that you're kind of framing it as a rhetorical question - i.e. you just came into the tank forums to bitch about a bad tank that raged at you rather than to ask an actual legitimate question.

I'm sorry you got a bad tank, and I'm sorry they raged at you. But no, it's not common practice. I make sure to tag all the mobs I'm picking up when I'm doing big pulls whether it be with a flash as I'm passing by or individually shield lobbing the ones I missed.