When a tank pulls small I roll my eyes. I only occasionally will dungeon tank when I'm in the mood as a raid tank main. So when a tank yaps at a healer to say "well why don't you tank" I'll say "k, back out put up a PF and I'll tank". Done it 4 times now.
The only time I will ever take it 'slow' is if my healer is undergeared or my healer can't keep up. Make the healers sweat is what I say, helps them get better and deal with stress if they plan on end game healing anyways.