Only because you're looking for feedback!

I'd personally move the party frames and any action bars that don't need to be clicked into less valuable real estate, like one of the currently empty bottom corners. A couple of your buttons could be combined into one (like using all your healthstones, your different mounts) and you might see if you can find keystrokes for some of your other skills so that you have a clearer view of "behind" yourself while tanking.

Looks super clean though, that's pitbull unit frames right? I really should bite the bullet and make the switch.