Chance to Block and Damage Blocked Formulas

[Mayunn]

I've been playing WoW for a while now, with kind of a blind eye to a lot of the math. However, the engineer in me has finally reared his ugly head, and I'd like to start running some calcs. Specifically, I have a warrior, and I'm thinking of speccing Protection for tanking... But I'd like to run some calcs to see how effective this would be, and/or which talents are most worthwhile from a damage reduction standpoint. Eventually, I'd also like to factor in importance of statistics (Agi, Sta, Str), to figure out which eq. is better for which purpose, and also resistances, and come up with some definitive Tanking numbers. There's a lot of information on this forum, and elsewhere, to get me started, but I'm having trouble finding anything on Chance to Block and Damage Blocked. So I was wondering if anyone could give me insight on the following:

1. How is chance to block determined? The Defense stat has some effect, but I'm wondering which other stats affect this, and how? Agi? Str? Anything else?

2. I know that Damage Blocked is a function of Str. But has anyone had any luck formulating this?

3. I'm not even sure how the Block stat found on shields works. Is this a straight damage number (i.e. my shield has a block rating of 35, so I reduce damage 35 damage per block? If so, can you get a "critical" block?) or does this also affect chance to block?

Thanks in advance for any info anyone has...

[Elethiomel]

1.
Chance to block is determined as follows:
(Assuming a player fighting a same-level mob)
5% base chance
+ talent modifiers
+ 0.04% per +defense

Agility influences your chance to block, but I don't remember off the top of my head by how much. Pretty sure it's at the same rate that agility affects dodge and parry, though.

2 and 3.
The shields block-value subtracts directly from damage taken when you block an attack. E.g., if you are hit for 70 points while blocking with a 35-block shield you will take 35 points of damage.
Every 20 points in strength adds 1 to your shields block-value.
This extra block from strength does not show up in any tooltip in the game.

- Elethiomel

[wathombe]

1.
Chance to block is determined as follows:
(Assuming a player fighting a same-level mob)
5% base chance
+ talent modifiers
+ 0.04% per +defense

With sincere apologies for performing thread necromancy, I have revived the only serious thread I could find here regarding chance-to-block.

I'd like a little clarification on the above, particularly the +defense portion. Is that +0.04% per point of defense skill, or +0.04% per point of defense over and above standard for the character's level (level*5)? I would assume the latter, else every lvl 60 character gains an automatic additional 12% chance to block, which doesn't sound right.

[Kail]

In a way, both. You gain the 0.04% for every point of defense you have, but that's countered by the enemy's attack skill, by the same amount per point. That's why it's easier to block (and dodge, and parry, and be missed by) things much lower level than you; they don't have enough attack skill to counter your defense skill. For the block chance that shows up in your 'spellbook', you'd have to have higher defense than the standard for your level to see a bonus, because that chance is calculated off of enemies your own level, with the appropriate attack skill.

[wathombe]

That's what I suspected. Conversely, when I'm tanking bosses in instances, my chance to block will go way down if they are higher than lvl 60 (as I have not spent talent points on or sought gear with +defense).

Thanks for the clarification.

[Gejt]

Agility does not influence your chance to block nor your chance to parry, it does however influence your chance to dodge (+20 agility equals 1% extra chance to dodge aswell as 1% extra chance to crit). 1 agility also equals 2 points of armor. This is for warriors, not sure about the numbers for other classes.
Your chance to block will go down by 0,6% (0,04 * 15) vs bosses which are considered level 63. As will your chance to dodge and parry together with an extra 0.6% chance to get critted.