Add one more thing to your list of what makes a good tank: the awareness of how to allow your dps to be most efficient. That means NO BLOODY SPINNING AROUND FOR NO REASON.

It's amazing to me how many tanks are either completely ignorant or just don't give a damn that melee dps has positional requirements. If you're not giving them room to get behind the target, if you're jerking the mob about (unnecessarily) so that they have to chase after its flank/back, you're severely gimping your group. Even the casters are affected by too much movement though granted not as badly as melee. So if you as a tank have never considered this, please do. If you know but don't care, please stop tanking.