I don't believe anyone has touched this subject, so I will.

As a tank, rely on your healer, but don't DEPEND on them. What I mean is, don't always expect a heal every god damn time. Some healers might be able, some, might not. For whatever reason, not every healer is the same. Keep track on your health and pop those self heals or potions. Don't be afraid to do so. Your healer isn't a god who can save you from everything. Do your best to relieve their stress as well. Sometimes aggro does get pulled, rare, but it happens. If you have been able to keep them in a great position by taking some of that stress away, they can help recover a stolen aggro, or from a terrible AOE that people couldn't dodge.