I understand the reasoning behind each option of gearing, but its all about picking what works for you and meshes with your group; which has been advocated but I think is worth repeating. If your group has pro dps, but are slacking on the healing front, you can gem/reforge/gear for more mitigation and survivability, as well as vice versa. I think we are better at doing this than any of the other tanking classes, and it's more noticeable to outsiders.
Blizzard has done awesome by me by expanding the role of a 'tank', and giving BrMs an incredibly high ceiling with which to maximize my potential. I have pulled off things with my BrM that I would have been hard pressed to do on my warrior or pally. It's all about adapting the math to your specific situation, and gearing for what works for you and your raid group.
I believe each story is valid, but unfortunately it's up to the individual to determine what is more valid for them the majority of the time, if that makes any sense.
Gynshon's previous post just helped what I'm trying to say.