For the most part your gemming/enchanting is fine, I'd suggest the following changes:
Regem the other gem in your chest to 30 stam also (unless you are going to make breastplate of the white knight, in which case put all +30 stam gems in that when you get it)
Enchant your cloak with 225 armor
Enchant your gloves with 240 armor
I prefer Tuskarr's Vitality to boots, but your call I guess.
Put 10expertise/15 stam in your gloves, or 10agi/stam or 10dodge/stam.
I'd also suggest getting indestructible plate girdle and spiked death dealers made. The mats aren't too bad (at least not as bad as the bracers/chest).
The main issue I think though is your spec.
I'd suggest the following: Talent Calculator - World of Warcraft
Deep wounds is a must for threat. If you need more, glyph devastate and vigilance.
Edit: OOH! Totally forgot: Trinket! Get rid of the ony talisman and pick up either essence of gossimir or glyph of indominability.