How valuable is mastery as a mitigation stat for a warrior tank?

Question

Can anyone provide some math on precisely how valuable mastery is as a mitigation stat versus the other mitigation/avoidance stats?

Note that I'm not concerned with how the different stats affect healers. I realize a less-spiky damage intake is better for healers, making mastery more desirable, but for the purposes of this question let's assume I'm just trying to take as little damage as possible.

Ideally I'd like a concise summary of the following for a 300 second patchwerk-style fight in a normal 10-man cataclysm raid:

1. Total mitigated damage per point of mastery rating with the block value meta
2. Total mitigated damage per point of mastery rating without the block value meta
3. Total avoided damage per point of dodge rating.
4. Total avoided damage per point of parry rating.

Here are my stats for DR considerations:

 - Armor:   35464
 - Mastery: 21.18   (2363 rating)
 - Dodge:    8.81   (850 rating)
 - Parry:   14.73   (1931 rating)

Let's also assume for simplicity's sake that I use Shield Block on cooldown.

Bonus points if you want to do calculations for a 10-man heroic and both 25-man modes.

Super bonus points if you can give me a concise formula (pseudocode, excel, whatever) where I can input my stats and output each of the values.

Answer 1

For protection warriors, Mastery is actually a great stat.

This thread on elitistjerks.com contains good theorycrafting data for protection warriors; particularly this section:

Survival Stat Priority:

Stamina > Mastery > Parry > Dodge

Stamina is still your best stat, but not to the extent of sacrificing everything else as was the case in WotLK. Conserving healer mana is a very real concern now. Mastery is your best stat for smoothing out incoming physical damage, and also increases rage generation through blocks. Parry provides the same avoidance level as Dodge now, but also procs the Hold the Line talent. Dodge will become more valuable as gear ratings climb higher to reduce diminishing returns losses from over-stacking the other stats.

For specific calculations, WarTotem over at TankSpot has made a lovely spreadsheet containing all the information you should need!

An important point is the "point of unhittableness" (ie when you have a combined chance of 102.4% to dodge, parry or block), at which point a boss can no longer "hit" you, only block dodge or parry. At this point mastery becomes an even better stat than it was before, since 60% damage reduction from a block is better than 30% damage reduction from a block!

You can also read through both threads for detailed discussions of the mechanics involved by people an awful lot smarter and more in-the-know than I am!

Answer 2

Here are the results I came up with using the spreadsheet referenced in Nellius' answer.

Damage Mitigated Per Point of:

Mastery w/ meta:  293.75
Mastery w/o meta: 284.27
Dodge:            328.03
Parry:            290.64

That's for a 300 second fight with full raid buffs, unmitigated boss damage of 110k, boss swing timer of 2.4 seconds.

The high value for dodge is probably due to my reforging choices. If my dodge and parry were split evenly (1390/1391 rating) here are the new values:

Mastery w/ meta:  292.79
Mastery w/o meta: 283.35
Dodge:            300.81
Parry:            317.01

It's also interesting to note that this change reduces the overall damage taken by 5725.6.

Obviously YMMV due to the overwhelming number of factors that contribute to survivability. Definitely use the tankspot spreadsheet to generate your own numbers.