That is, in fact, the way to calculate it. With the exception of critical block, mitigation uses a one-roll system, so you do not have seperate rolls for each type of mitigation.

2shared - download mitigation.xls

Here is my mitigation spreadsheet at the moment. Put your stats in at the yellow part. Swings/HtL is a value you supply which basically means any given time you are attacked, how many attacks have you received in the last 10 seconds? This is an estimate which varies by encounter. It's a lot higher if you have many adds to tank, and a lot lower if the boss frequently takes breaks from attacking. There is also a field for Night Elf racial. Set it to 2 if you are are a night elf and 0 otherwise. I haven't modelled any other racials such as stoneform because (in the next patch anyway) they will just be a static damage reduction that won't impact your gearing priorities.

There are three tables at the top, which show calculations for no meta gem effect (if you are using mastery and run speed for instance), the block meta, and the armor meta.
At the bottom of the sheet, you see stat priorities. These are given in amounts of equivalent armor. Just consult the row depending on which meta you are using. There is also a small section showing how much each meta is worth, if you are trying to figure which one you prefer.

Things to work on-
Are crit blocks with the meta 61% DR or 62% DR? My spreadsheet uses the latter, but I'm not sure.
I don't have any nice way to model trinkets and procs. Maybe in the future.
It's not very pretty. Deal with it =)

How closely are we able to model parry lost to DR at this point? I haven’t seen a formula, is there one that is known? If not I have a messy polynomial that I generated from approximately 100 test points that to within an accuracy of 0.01% will predict actual parry % when passed pre-DR parry % within the range I took samples from (0 to 2300 parry rating). If anyone is interested in seeing any of this work let me know and I’ll make it available, or if a formula already exists please share.

For Al'akir, what do you prot warriors do in phase 3? I had switched to berserker stance and started spamming Col. Smash and Execute. I had assumed that would have been better dps. However, I now think it may be inferior to Devastates and Shield Slams. If others could share what they do during fights such as this (or any other time they find themselves no longer needed to tank in a dps race phase) it would be greatly appreciated!

Thank you. However, I have looked around WoLs and find that not every warrior execute spams in phase 3. I am wondering if there is a general consensus on what the optimal rotation/priority would be in this situation. If this has not yet been determined perhaps we should discuss our opinions on it.

As a man of old habit, I switch into Battle Stance (back when 10% ArP > 3% Crit), but I think it would mostly depend on your rage generation in Phase 3. In Berserker Stance you can still Dev -> Dev -> SS* and Execute with high rage to probably great effect, but using Rend is more DPS than a single Dev, so it could also work that jumping in Battle Stance and going Rend -> Dev -> Dev -> SS* with high rage Executes may work out better, not forgetting that with the Blood and Thunder Talent (2/2), your Thunder Claps also do a damage tick of rend along with the TC damage, and keeping Rend up this way will eventually result in you using Shockwave if specced Thunderstruck.

Personally, I prefer going into Battle as said earlier, but that's always because I'm always Shattering early into P3 when all the physical DPS is (hopefully) alive and Recklessness is still on cooldown from the pull.

* Depending on SnB procs, obviously, but still highest priority.

Ok, so most ppl would agree that Stamina > Mastery > Parry >= Dodge. But I cant find any up to date info on stat weight. I agree that 100 sta is better that 100 mastery, but is 90 sta better than 110 mastery? or 80 sta better than 120 dodge? or parry?
The default stat weight on wowhead is, for the lack of a better word, bad. For example, the 2nd best chest and legs (<372ilvl) is hunter gear. Its Mail with agi, hit and mastery. It scores agi and parry with the same weight. This can't be right.
I think most casual people (me included) would really appreciate and accurate stat weight. Even if there needs to be 2 weight sets taken into account. One before expertise and/or hit cap and one after.

First of all, there is no reason anymore to cap hit and softcap expertise unless you find yourself needing more threat.

Comparing stamina to mastery/parry/dodge is comparing apples to oranges. What you need in terms of hp depends on the encounters you're doing and other individual factors.

The usefulness of parry/dodge/mastery varies with your gear and can't be summed up in a stat weight. The good news is that mastery is generally more useful than parry/dodge (though it is not necessarily more damage reduction). That only leaves the parry vs dodge question. The simple answer is keep dodge somewhat lower than parry. The more accurate answer is you need a spreadsheet to calculate which is currently better for you.

I assume this will end the war over which is better...

Is that truly a nerf, or simply a tool-tip fix? Because isn't it doing 1% atm?

At a guess, the comment about hit was because taunt is now auto-hit so the only benefit from hit/expertise is additional threat