Still waiting for the extra 1-h weapon to start looking at Single-Minded Fury. But I did start working on my tanking again recently. I went back to September to look at Theck's posts on warrior mitigation statistics and started thinking about how warrior gearing works now. To oversimplify for convenience, the value of our various active mitigation statistics and our passive avoidance statistics varies depending on how you prioritize Shield Block and Shield Barrier. This means, among other things, that you can gear, gem and reforge differently if you intend to be running primarily five man dungeons vs. raids, and that you can even change your tactical outlay of stats based on whether or not you're running 10's vs. 25's to some extent.
Really, what it comes down to is Shield Block vs. Shield Barrier use and the tension between trying to avoid the absolute most incoming damage vs. trying to create the most predictable spread of incoming damage. Theck makes the point that, while spamming Shield Barrier might cause you to take the least amount of damage overall, you're going to end up taking spiky damage. Spiky damage is something healers hate. A healer would much rather you were taking hits that kept you constantly losing about 60% of your health than be in a situation where most of the time you took no damage, but occasionally you took 90% of your health in one hit, especially when those hits could occur back to back.
As a result, while it may be mathematically best to rely on Shield Barrier, it won't work out that way in actual practice because healer mana isn't infinite and they can't just bomb heal you to full if you go down to almost dead in one or two hits. Damage spikes are the enemy, and a balanced use of Shield Block and Barrier will cause your incoming damage to be far more predictable and easier for your healers to cope with.