place only gets worse when you do bring in healers

Are you starting to see the problem? Even on their OWN metrics, DKs are going to have a very hard time responding to incoming spikes appropriately, a problem that "automatic tanks" simply will not have because they won't be getting spiked in the first place. Even before we bring healers into the argument, DKs are in an inferior place to non-dk Tanks, and that place only gets worse when you do bring in healers.

Now maybe you do or don't (will or won't) euwowgold tune fights so tightly that it will matter. That doesn't change the fact that are markedly less effective as tanks.

And before we go down the road of "well magical damage" let us not forget who the reigning "god" of magic damage mitigation is: the DK. Or are you suggesting that we're back to "niche" tanking designs?