Fine in theory, but remember, parry isn't the same as dodge or miss, it speeds up your next swing, and there will come a point in raiding, where you'll want to block a few less times (think Prince phase two, when even If you block them, he can lay 22000 points of damage on you in 2 or 3 seconds) and parry and dodge as much as you can, and make up the difference in threat gen with extra spell damage.