Oh, so you really were taking about keeping enmity as a "primary focus" o_O
So, again, keeping enmity is only very loosely based on how much damage you actually do. By that, I mean that you could be absolutely horrendous at dealing damage that you would still be top enmity, simply be being in your tank stance. So, that whole "I'm min-maxing my rotation and it should reward me more than healer pushing one button" is completely irrelevant there.
So, I'll say it again, optimizing your damage has nothing to do with any primary focus of a tank, be it keeping the enemy on you or surviving attacks. And they pretty much don't interfere with each other, as opposed to healer who need to "sacrifice" some GCD to deal damage, and could potentially not heal enough if they're too greedy. That's why it make more sense to me that a healer who take that kind of risk should achieve higher numbers than us, since we don't sacrifice anything to push our damage. Funnily enough, if you look at the graphs that were posted on this very thread, tanks in SB were far above healers when it comes to DPS, and they had to sacrifice something for that, namely, their tank stance.