The most important thing when it comes to tanking is knowing what you are doing, whether you be Warrior or Druid -or for the hell of it Paladin-.
If you are a Warrior, you need to know exactly the situation that calls for Shield Wall, or if Druid when to back away a few yards -shift -innervate priest -shift. You may lose a lot of rage in shifting to innervate, but that can be considered expendable since the style of take the beating builds more rage quickly. Remember, most fights have a small window that the boss or other mob does a special move that can be exploited. Another Useful thing for tanking Druids, that is little appreciated among them, is Feral Charge; if the mage or priest pulls aggro, how ungodly useful is it to have an instant intercept that you do not need to change stances for.
Gear is highly important to a tank, no matter the class, but druids can get away with lower quality than a warrior in many cases. We also do more damage tanking, though that is balanced in other ways.
Personnally, I prefer Druid tanks since they understand healers better, since most of them-including myself- were forced into healing. I only blame the healer for the wipe in the case of him not paying attention, either by going afk unannounced or by not following me to the rift in Black Morass, instead farting around looting the last corpse.
I have not tanked any raid bosses yet, but being my guilds main tank, we will be starting Kara, probably by the end of the week, so...
Be back then