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.
The more mitigation you stack, the less healing you need. The less healing you need, the less stress is placed on healers. The less stress is placed on healers, the better the raid does. Stacking DPS would not help a tank much. We have abilities that do way more threat than damage, and don't really have skills or bonuses conducive to good dps.
You're better off letting the healers throw some DPS in because they don't have anyone to heal, really.