If you were main tanking you would be better off with Pillars of Might and a 4pc tier bonus. Aside from that perhaps some slight spec/glyph changes, but those are more personal preference things.
To be honest I wouldn't change a thing. You stated you have a niche role in your guild and are set up for the task. Good tanks tailor their set up to the fights they are pitted against and what the guild needs. Who could ask for more?
There is something so appealing about backhanding someone across the face with a shield.