"The plate +defense gear's been going to offspec for weeks, but the hunters get dibs on the next Twin's Pact or Hellion Glaive, and the rogues are still rolling on non-set. We need another tank, but they'll just respec one of the death knights for the next boss."
Remember what we said about #3? Plate tanking gear is stuff that absolutely no one else in the raid wants, and it goes to offspec pretty quickly as a result. It's for this general reason that it's easy to gear a holy paladin, resto shaman, resto druid, or plate tank; the competition for their gear is limited (when it exists at all). An Arms/Fury warrior, Retribution paladin, or DPS death knight will have little difficulty assembling a decent-quality offset once the regular tanks have their drops. By contrast, a non-Feral druid who wants to tank is at the back of a very long line comprised of the raid's tanks, melee DPS, and hunters before they'll get a crack at rings, cloaks, trinkets, necklaces, leather DPS gear and weapons.
My take: This probably does have an impact on who's most likely to get a shot at tanking from within a raiding guild if an existing tank has to retire or goes on break. While it wouldn't explain the immediate decline of bear tanks, it might play a role in how likely we are to bounce back. As with #3, it's a problem that eventually solves itself given a sufficient amount of time spent farming a raid, but odds are still pretty good that a plate DPS class is going to finish and update a viable tanking set long before their druid colleagues do. Ergo, the first option for a "replacement tank" within a raid is likely to be another plate tank.
Complaint #8: A druid who's dual-specced into healing or DPS has more difficulty returning to tanking than other classes.
"Look, I know you really want to tank this fight, but all three of our tanks have excellent attendance and I don't want to leave any of you out of the raid. The warrior's going to tank, the pally's going DPS, and I'd like to have you come boomkin or heals because melee sucks on this fight. Would you seriously rather be benched?"
Balance and cat DPS were both hugely improved in Wrath, and Restoration also had two prayers answered in the form of a flash heal and a group heal. Between that and the introduction of dual specs, druids are in the position of selling themselves out of a tank job if they become known as a competent DPS or healer. They're also the only tank who can spec into ranged DPS or efficient group heals, and both can be huge advantages in melee-unfriendly fights and encounters with high raid damage (which these days is close to being all of them).
And -- remember points #3 and #7? -- there's limited competition for leather +spellpower gear in the raid. Any druid who's been raiding for any length of time can build a decent healing set just as quickly as a plate DPS can build a decent tanking set, and should be able to jerry-rig a functional moonkin or cat set with some effort. Depending on your competition, it may actually be easier to build a Restoration off-set than it is to upgrade your tanking gear.
My take: I honestly think this is the single most important reason behind the disappearance of the bear in raid content. On a more depressing note, it's also completely unavoidable.
It's somewhat related to #5 -- as we've observed, many of the advantages conferred by the use of a bear tank are advantages conferred by the use of a druid, period, and it's a lot easier for Balance, Resto, or cat druids to heal, battle-res, and innervate. That's a strike against us on any fight where the opportunities to pop out of bear are limited (if they exist at all), but oddly enough, tank parity is an equally significant disadvantage. If no tanking class brings any particular advantage to a fight, a raid leader's thought process is pretty straightforward. They're people too, and most of them don't like the idea of benching a consistent raider. While most raid leaders in serious raiding guilds grudgingly benched part of the tank corps in classic and BC content to build a raid for 1- or 2-tank fights, they don't have much reason to do so in the age of dual specs. What's your second spec? Come as that.
Ghostcrawler's referenced both the continuing popularity of the warrior tank and the death knight's having carved a niche for themselves in Wrath tanking, and what I think is happening is this; the Protection warrior spec and the death knight as a whole have both enjoyed explosive popularity since Wrath went live, and in the months after the expansion's release, complaints about a tanking glut started to surface with unnerving frequency on the Tanking forum. Paladins and druids are being squeezed out of tank positions, not because they're bad tanks, but because there is enormous pressure on these players to respec and come as something else when it's either that or get themselves (or their warrior/DK colleagues) benched on a fight.
Anyone who's played a druid for any length of time will recognize the classic dilemma; do I respec so the group/raid gets off the ground, or do I hold out for my preferred spec and force the group/raid to build around my preference? I've always picked the former, and with the way that druid spec numbers have ebbed and flowed over the years, I don't think I'm alone in that. Unfortunately, when it comes to tank numbers, this does mean that population balance isn't likely to happen anytime soon; the odds of your tanking an encounter are determined more by the overwhelming popularity of plate classes than your actual skill at playing a tank.
Every week, Shifting Perspectives treks across Azeroth in pursuit of truth, beauty, and insight concerning the Druid class. Sometimes it finds the latter, or something good enough for government work. Whether you're a Bear, Cat, Moonkin, Tree, or -- for some unaccountable reason -- stuck in caster form, we've got the skinny on Druid changes in patch 3.2, questions and answers on new Bear and Cat forms, and thoughts on why you should be playing the class (or why not).