Quite a lot of discussion on tank balance, not just pwnwear, wow.com had a (good) post on effective health and also Ghostcrawler’s posted on it.
Here’s an extract from GC, but he said a lot more, worth checking the source too.
On Sartharion +3, cutting-edge guilds who normally tank with a warrior would (perhaps somewhat begrudgingly) use a DK to tank instead because the benefit was so massive. The same thing happened on Vezax where good guilds replaced their warrior tanks with DKs. Death knights were overpowered at the time.
We are not seeing the kind of massive swapping one class of tank for another in ToC or the preliminary Icecrown testing. It’s just not happening. If paladins or druids are too good or warriors or death knights aren’t good enough, we’re just not seeing them getting used for those fights to anywhere near the extent that DKs replaced other tanks on the encounters mentioned above.
Warrior tanks can tank every boss in the game, and more often than not get the world first and server first kills on those bosses. More raids use warrior tanks than any other. Most cutting-edge guilds use warrior tanks. We can’t detect a higher “failure rate” on warrior tanks, and frankly I’m not even sure what that means given that most everyone here agrees there are far more experienced warrior tanks than other tanks out there. Some of you are arguing “when we switch to the undergeared paladin, we do better,” yet very few groups are actually switching. The best we’re stuck with is some kind of fuzzy “it’s harder on the healers,” which is pretty hard to quantify, especially since the healers aren’t running out of mana healing anyone.
This is why the developers keep going back to what we are seeing happening in the game, which is warriors tanking stuff.
[...] Yes, if we see paladins or druids (or warriors or DKs for that matter) repeating what happened on Sarth or Vezax, then we will do something while Icecrown is still relevant.
When is the appropriate time to buff or nerf is something that is always going to be subjective. Buffing someone when we aren’t convinced they need it (assuming it affects relative power compared to another class) is as dangerous as not buffing someone when they do need it.
And again, it’s not as simple as guilds having a favorite tank for specific fights. Druids on Thorim or warriors on Anub adds didn’t cross the line for us, though I understand why it might for some people.