Steave, I don't think you understand the point of my post...which is...how much tank gear do you actually need to be an effective tank. Because adding additional tanking gear beyond that point is unnecessary and you might help your op team more by increasing your dps.
Put it this way. HM ops KP and EV were designed for tanks in level 56 gear. Most of these tanks are now running around in mostly level 61 gear. Instead of over-gearing they could be increasing dps.
Like Mantorock says, stacking more mitigation at that point will increase the raid DPS more then having you add some DPS gear.
If you take less damage, the healers don't need to heal as much and can thus do some dps, but the difference is that healers stacks the same stats as DPS (power, crit and surge, the only difference being alacrity instead of accuracy) so they'll do more damage than you.
Therefore, gearing to increase your DPS as a tank is never
a good thing. Use your abilities properly and you won't loose threat, and the raid DPS goes up more as you free up your healers.