Three Tanks walk into a bar...no that wasn't it. Oh yeah, I remember now. Three Tanks walk into a 25-player raid...and it doesn't matter which class they are.
The other day, at lunch, it was posited that have a mix of Tanks was important. Six months ago, I probably would have endorsed that, but when I think really hard about it now...not so much.
Homogenization of the Lich King
During Wrath of the Lich King (WotLK), we saw great strides towards homogenization of classes, which Blizzard referred to with the catch phrase, "bring the player, not the class". This has two chief consequences:
- Raid groups (and guilds) can worry less about getting every class into their raids, so they can be more tolerant of class mix
- To achieve this, classes require greater homogenization (shared/redundant abilities), which makes them individually less special/unique
I say that, because, for the most part, they went away in WotLK and, by the time Cataclysm hit the shelves, we had seen some rather dramatic changes from what we remembered.
The New Era of Tank "Mix"
The premise that you want a mix of Tank classes rests upon the diversity they bring to the raid in terms of game mechanics. This begs the question - in what ways do they differ?
Debuffs are where we see some of the canonical Tank abilities.
- Melee attack slow - all Tanks can slow their primary target; Warriors and DKs can easily slow multiple mobs (at the risk of breaking CC). The latter is nice, but the former is the critical capability, and DPS DKs can provide the latter too.
- Physical damage reduction - all Tanks can reduce the Physical Damage they take; Warriors, Druids, and DKs do it via an AoE, Paladins can apply it to one to three targets at a time and that's plenty. If you were to rely on DPS to help, Paladins and Feral Druids could maintain it on their target without DPS impact; Warriors could do it with negligible DPS impact; but DPS DKs rarely dip into the second tier of Blood, so I would not expect them to be able to do this.
- Armor debuff - This is pretty important and, surprisingly, it has not made it to all Tanks. Only Warriors and Druids can do this right now. The good news is that this is a DPS concern more than a Survival concern (and yes, the fast the boss dies, the better). Rogues, DPS Warriors, and Feral Druids can provide this debuff, but it is generally less of a DPS impact if provided by the Druid, since Faerie Fire (Feral) lasts for five minutes and it is not uncommon for a Raid DPS Feral to have the Talent to apply all three stacks at once. Warriors and Rogues would need to re-apply more frequently and for Rogues, the need to use a combo point and a finishing move makes this relatively costly.
- Casting speed slow - This is an interesting ability that only one Tank can do - DKs. That said, I am not sure how desirable it would be to work Necrotic Strike into a Tanking rotation. Arcane Mages and all Warlocks can also provide a similar debuff, as well as Rogues (Mind-numbing poison), which increasing impacts on their individual DPS.
Your Raid Needs Class Coverage, Not Your Tank Corps
The title says it all, really. The buffs and debuffs are plentiful. Your real concern in class coverage should be aimed at making sure your raid has what it needs, not your Tank corps. So, if you have three Tanks all of the same class, that may be just fine, as long as your raid covers the buffs and debuffs you need.
Is There Any Reason to Have a Specific Tank?
For the most part, not really. We all have ways to address what we need to do. Picking up multiple mobs as range is still a little challenging for Warriors and Bears, unless charging in and smacking the mobs is OK. That said, in most cases where you need to Tank at range, a ranged DPS may be the better choice.
Sure, there are subtleties, but again it comes down to your raid. For example, if you had no Rogues, Warriors, or Druids at all in your raids, then maybe you would ask a Hunter to bring a pet that provides the armor reduction.
Some of the buffs are less distributed. The armor *buff* is only brought by Paladins and Shamans, as is "push back" protection for casters. The stat multiplier provided by Druids and Paladins can also be provided by a Shale Spider pet. But if you have none of the three, then no stat multiplier for you. For the most part though, you would need to be missing at least two classes completely from your raid before it was an issue.
So, yeah, don't worry about diversity on such a granular level. If your raid has the class abilities covered, you should be good.