Last night, I ran regular Culling of Strat. through the LFG system. It was a good run. However, the tank lost aggro a few times, and I found myself with a couple elite scourge minions in my face attacking me. He kept apologizing, saying he's new to tanking. I told him no worries. We killed the mobs, and nobody got killed. The fact was, he was trying to play his role properly. I ran heroic Gundrak one day with a tank who could not hold aggro for anything, and blamed us for wiping (why does it always seem these "elitist" players are the ones most clueless).
The fact is, we cleared the instance easily, and the tank performed his role. While he may have been unable to keep aggro a couple times, he did well, and was trying. I can relate to his situation as a DPS hunter. I've gotten better playing the class, but when I was in my late 70s, and then 80 running instances, I really didn't know how to play the class (though the tank seemed to).
In the end, when players make mistakes, it's best to be patient with them. After all, as long as nobody wipes continuously, and the players make an effort during the runs, that's all that matters. I have no patience for "elitist" players who harp on small mistakes, DPS numbers, etc. I am patient with players who may still be learning, and are making concerted efforts to try, because from personal experience, I want to make the runs a pleasant experience. The elitist types turned me off from instances for nearly two months. I don't want that to happen to other players.