Everything looks on track to me. I'd stick with the stamina since that generally adds up faster than any amount of avoidance you can get from gemming.
Enchants are standard tanking enchants. All good.
If you can reach the defense cap without stone gargoyle and pick up the 4% parry it does offer a small increase in avoidance. But I've had a hard time finding a way to fit it in myself.
I have almost the same tank gear and I am comfortably MT'ing in Naxx25, and Ulduar 10. We don't clear Ulduar 10 but for the 4 bosses we do.
I couldn't see your weapon because you had some level 1 lance in it but a nice weapon helps. Death Bite or above.