Tanking and MasteryFollow

When you have Best-in-Slot and trying to min/max, a lot of things change. This whole bit will depend mostly on your gear level. It's quite possible that even with a lower health pool you will net more Physical Survivability through Mastery, one must remember all the other benefits that Stamina grants as well as the non-physical damage a tank encounters.

Hit points are a much more versatile survivability buff, but there is a tipping point at which it becomes much less survivability versus physical. I would actually venture to guess this is even the case with Parry and Dodge. I would recommend, however, that you are comfortable with your health pool before venturing down Mastery Stack Lane.

If you are (I can't see your gear but your Ret gear is up there), then I'd say Mr. Robot has a valid point.

That's pretty much the gospel of maintankadin too, with some people even going so far as to ignore any means of additional stamina (reforging, gems, chants, and even trinkets) in favor of mastery when possible and a dodge/parry blend when not.

It's really not new theorycraft, but old (school) - the concept is that unblocked hits in Cataclysm are basically what crushing blows were in BC. So you accept a smaller health pool in order to maximize your combat table coverage, so you take fewer spikes. This makes you more consistently healable and in less danger of a string of bad RNG.

Not bad not bad (looking at your gear)!

I would say you're quite ready for Mastery Stack, however you definitely need to upgrade that tricket.

Both BoT and BWD drop nice tanking trinkets, and so honestly either one of them will provide you with a great enough Stamina boost that you'll have plenty of wiggle room in the HP department.

Honestly, where you're sitting right now, I'd just leave what you have and as you grab new upgrades, replace the Gems with Mastery or Mastery/Stam. The reason being: what I'm starting to realize from both the Tanking and Healing perspective in raids is that the Main Tanks gear isn't even all that important. S/He's actually one of the least important players gear-wise.

The encounters are set up to be doable even with pretty crummy stats as long as you do them right, and a lot of the killshot mechanics cannot be avoided even with an obscene amount of gear. Only places I've seen gear even making a difference thus far have been Halfus and the add tank for Maloriak.

Some of the bosses are literally jokes. This is not to say that your stats do not matter or that you should not be maximizing your survivability, only that you shouldn't lose sleep over it either.

We've downed Magmaw quite a few times (lost count) and I've only seen it once, but our Group 1 (I'm in BSquad) had it drop the first 3 times in a row.

Much luck to you! Also: if the BoT Trinket (Vial off Stolen Memories) drops makes sure to make your case that the 2 stacked up together is relatively pointless and a net loss of survivability, so see if you can finagle it out from his greasy paws.

Personally, I do prefer the Symbiotic Worm, though.