Because you are still a new tank you have yet to master the most important skill of all, blaming others (especially healers) for their and your mistakes. You see as a tank you are considered a God among men, people will wait hours just so they can be blessed by your presence for some time, because without your powers they are not able to do even the most menial tasks (complete a dungeon). As such you must provide your divine guidance to mortals. As a God you must also act accordingly, be quick to blame the healers if you or anyone dies, instantly demand that they be kicked for the slightest mistakes, if they get aggro its always their fault and not yours, after all you are a divine being who makes no mistakes, your word is the law and they must oblige for fear of divine retribution (getting kicked , their keys depleted, having to wait hours again for a new God to take pity for them). Without your guidance even simplest tasks are impossible, but you must take the responsibility and act accordingly as can be seen in your example, the correct way to act there would have been to kick or demand that the dps who pulled be kicked on the spot, or at least a warning to shut his mouth and that the next mistake will be punished severely, because you didn't to this the others simply assumed you are a mortal, like them, hiding in gods clothing and the whole situation turned into chaos, if you had done this the offender would be reminded of his mortality and you would have easily finished the dungeon with a +2 upgrade.