Gem priority: Stam. Always stack stam. If you need to meet a meta, use whatever/stam.
Enchant priority: Stam.
Like others have said, you should be getting all the avoidance you need from your gear. I appreciate that you "have a feeling" that you need avoidance rather than stam in ICC. You don't. A lot of things are unavoidable. You can't parry spells.
I single tanked Lord Marrowgar in ICC a few days ago, in a pug raid, where the healers were considered undergeared for the instance. I didn't need to gem for parry to do it.
Sorry if I come off as sounding like a prick, but it's starting to get to me, reading all these people who are new to tanking/dps/healing/whatever here, on other forums, and in the game, saying that they won't go with what's been proven to be better just because they have a feeling.