Why do I need naxx gear for heroics?

I did a slow, but steady Naxx 10 PUG this afternoon and managed to win Repelling Charge. This is perfect for my heroic set. Why do I need it? Well...

Now I can hit the raid defense cap while not wearing pants. I can also hit the heroic cap while using TF and also not wearing pants.

So next time you see someone indirectly claim that you need raid gear for heroics, accept that they are right and they're just trying to do it with style.