Here is our rough math on how to weight stats for tanks, until we find another source that gives us some convincing values.Protection Warrior
Dodge = Parry, but parry gets a bonus for warriors because they get +10% critical block chance proc on parries.
1 point mastery = 1.5% block and 1.5% crit block. So,
1 point mastery = 1.5% block + (1.5% of [current block] extra blocks) Or,
1 point mastery = ~2% extra block, since warriors have a base of 27% block
A block is 30% less damage on an attack which is the same as saying:
Block is avoiding 30% of an attack
Dodge is avoiding 100% of an attack
Parry is avoiding 100% of an attack
If your parry is high enough, prot warriors have a talent that gives +10% crit bock buff for 10 seconds. The up time would be high on this in a raid scenario. So, if we figure that in:
Each mastery point is 1.5% more blocks, but a flat extra 10% of those are going to be crits. So add 0.0015 per point of mastery. (Keep in mind this is rough.) So,
1 point mastery = 2.15% block.
Multiply by 30% to compare to dodge:
Mastery is 64.5% as useful as dodge for overall damage avoidance.
25% of strength is converted to parry rating. We can take the strength on gear and multiply by 1.05 for raid buffs. Call it 26.25% of parry.
We can roughly equate this to avoidance. Avoiding 2% attacks is like taking 2% less damage. But, armor is not a linear calculation. There aren't many items with extra armor. Just a couple trinkets. We are OK with a rough estimate here:
1500ish Armor to get 1% damage reduction in the 55% range. So, 1500 armor is roughly equal to 177 dodge rating. This then has to take into account armor multipliers like toughness or the various bear form multipliers to come up with a decent ratio between armor and dodge rating.
Expertise and Hit:
These are apples to oranges. They can be weighted independent of mitigation stats depending on how important you feel they are. Expertise should always be double hit rating before the dodge cap. Unless I am mistaken, parry haste is no longer an issue, thus neither stat provides any damage reduction.Protection Paladin
Parry is identical to dodge for a paladin
All other rules are the same: strength, expertise, etc.
1 point of mastery = 2.25%
Paladins block 40% of dmg per block
1 point of mastery = about 90% of a dodge.
Mastery should be 90% the value of dodgeDeath Knight
There is a debate on the relative value of avoidance, mastery, and stamina. For our stat weights, we've chosen to value avoidance > mastery > stamina for the stat weight purposes. Why?
1.) Healer mana IS an issue right now in the game. Avoiding and/or mitigating damage is going to be extremely valuable in difficult raid encounters. Having a huge health pool is great, but right now we aren't seeing tanks dying from getting one-shot, we're seeing tanks dying because healers fall behind.
2.) At current gear levels, the diminishing returns on dodge/parry aren't that pronounced. At the next level of content, we will probably want to specify some sort of "soft cap" for dodge/parry after which we value those stats less.
3.) As far as whether to consider mastery or stamina better... this really comes down to gem selection. All gear at a particular item level has the same amount of stamina on it, with the exception of trinkets. Swapping mastery and stamina stat weights will not affect your total gear that significantly. Lets look at the relevant gems (only survival-based gems):
red: +40 Parry
yellow: +40 Dodge, +40 Mastery
blue: +60 Stamina
orange: +20 Parry and +20 Mastery (I don't think the new Parry/Dodge "stalwart" gems exist in the game right now)
green: +20 Dodge and +30 Stamina, +20 Mastery and +30 Stamina
purple: +20 Parry, +30 Stamina
So, how do we want to gem? Red sockets will be Parry. Yellow sockets will be Dodge. Blue sockets are the only ones to worry about, and we're only going to have a few of those. With the stat weights that we have chosen, you will end up with Dodge/Stamina or Parry/Stamina gems.
For trinkets, our stat weights will favor a trinket with Mastery over a trinket with Stamina, but, in reality these are the trinkets you are considering at the 359+ item level:http://www.wowhead.com/item=65048http://www.wowhead.com/item=65109http://www.wowhead.com/item=58182http://www.wowhead.com/item=62048
So, you're really always going to end up with the symbiotic worm and vial of stolen memories at 372 item level. The choice is going to be less clear at item level 359. Bedrock Talisman could be a better item than the symbiotic worm. We aren't considering the darkmoon card as superior because of my first point.
So, in the end, the stat weights we are using will not massively change your total value of stamina vs. mastery. You could swap the two if you prefer, but the overall effect on your gear is going to be minimal.