Generally speaking, mass pulls make the most of the dps' toolkit as well as scale better with the healer's capabilities, so it's expected for tanks to do so. Of course scaling pull size to the dps and heals is necessary considering wipes are a much bigger waste of time.

On a side note, why are people getting so upset over this that their first reaction is sabotage or refusing to play? Two wrongs don't make a right and all poor party play does is make victims of the other two people in your party. If it's that upsetting that the tank isn't up to snuff then either put the time into teaching (provided the tank can listen) or feel free to leave the dungeon.