Perhaps the single most annoying thing about Druid tanking is our gargantuan ass. As an elf, it's perky and tight and I can see around it and all is well. But the instant I drop into Bear form, it's all ass all the time...and it's hairy.
The worst part is when you get backed into a corner or have to fight in confined spaces where you can't scroll out to give yourself the same real estate of view any other character might take for granted. For this reason and this reason over all others, I nearly dropped my Druid tank for a Warrior. There are, to be certain, other reasons to select a Warrior over a Druid when picking a class to tank with, but this is one of the biggest. Still, if you can get past the fuzzy rump in your face Bear tanking is incredibly satisfying.
Why would you pick a Druid tank over a Warrior tank if what you really like doing is tanking? After all, Warriors get plate armor, shields, ranged weapons, a single form to manage, a fear break, no expectation of healing or buffing, a vast array of tanking tools, the mechanics for parry and block, and the comfort of a community that regards them as indispensible in the role of a tank, a guaranteed spot, if you will.
Bears bring a few unique tools to the table such as immunity to polymorph effects, a charge indifferent to stance, massive armor totals, pre-combat buffs, and frequently larger health pools. Doesn't look like much does it? In truth it isn't, but it's the balancing act that Druid tanks endure for the versatility of roles they enjoy in contrast to the Warrior's versatility within a role.
Rather than focusing on what Druid tanks don't get, we're going to look at making the most of what they do.
First and most noticeable are the massive armor totals Druids enjoy. A comparable Druid and Warrior will see an average of a 10k AC difference in the Bear's favor. As an example, in gear that largely outclasses mine, my GM runs around 9k less armor than I do at the time of this writing. On the surface, this difference is huge, but the way the armor formula works, this is about a 10% difference in damage reduction.
So the big question that arises from this is: why? Why do Bears have such massive armor totals? There are several possibilities, but one stands out more than the others.
While Critical Hits (200% damage) are eliminated through Defense, Talents and Resilience, Crushing Blows (150% damage) are mitigated by Warriors and Paladins via their shields. Bears eat them. Bears do not have access to shields, and hence have no access to block. In theory this was mitigated in the past both through higher armor totals and higher health totals. In practice, Bear and Warrior health totals are getting more and more in-line leaving just our incredible armor to compensate while we take the Crushing Blows a Warrior can potentially push off the hit table.
So again: why pick a Druid over a Warrior?
Well, mechanically this isn't a question I can answer. Most Druid tanking advantages are designed explicitly to make up for fundamental class and gear differences. Certainly stylistic differences can make a case, but I pointed out at the beginning what I think of my Big Bear Ass (tm). Warriors are, on the whole, better designed for the role.
Well, hopefully I can work to provide an answer to this while also providing meaningful commentary on Druid tanks, the culture that surrounds us, and game mechanics. Every Druid tank will encounter bias no Warrior must deal with, unrealistic expectations, lack of in-game support for the role, and bizarre resentment from the most unlikely quarters.