A few thoughts here...
- You shouldn't be gemming for parry with your stats. If you need the defense in a red socket, use a Stalwart (dodge/defense) gem. (i.e., your chest) Ditto for not using a straight parry gem at all; go dodge, or dodge/stamina, or just stack stamina (i.e., your gloves).
- You could stand to rebalance your gems overall a bit as well. For instance, if you need the defense, go defense/dodge in your gloves, so that you can go straight stam in your belt. Or alternatively, put your green gem from your belt in your pants, and the stam gem from your pants to your belt. Then you're just a red/purple gem away from a socket bonus in your pants, and you haven't given up anything yet. Ditto for your boots.
- Your chest isn't enchanted. A +22 def enchant there would give you a LOT more leeway to gem dodge/stam and defense/stam in your red and yellow sockets, picking up a lot of +stam socket bonuses (not to mention stam overall).
- You need shoulder enchants.
- Glyph of Seal of Vengeance is *FAR* more effective for threat (and also partially for indirect mitigation by reducing parries and boss parry-haste) than Glyph of Judgement (assuming you want the utility of Glyph of HotR).
- Minor glyph of Sense Undead - free tps and dps against undead mobs!
- Your spec is a little odd. A few items here...
- The armor bonus from Imp Devo is valuable. You should be 3/3. (Not to mention the healing bonus if you don't have a resto druid)
- Unless you ONLY ONLY ever off-tank, you should REALLY have Judgements of the Just. It's a big deal for reducing incoming damage from bosses.
- You really only need 1/2 Imp Judgements to keep up a proper 969 rotation
- You should really only need 1/2 Spiritual Attunement, and also don't need points in Benediction at all (unless you use 1 point as a filler to get to the 3rd tier in ret). If you're having mana problems, this implies you need to work on keeping your Divine Plea up more effectively, not that you should spec more for mana regen/reduction.
I hope that helps a little!
Edit: My armory is in my signature, although I don't have my standard maintanking gear set equipped. I logged out in my "spiffy" set.