Comparison of 3.2 block and dodge

[Stengel]

Introduction
This is an attempt to gain some insight into how good block value as an itemstat is really going to be for warriors.

In patch 3.2, given 100 item budget points, one the following stats could be gained from two different hypothetical items:

a) 100 dodge rating, which, applied to a warrior with already has 400 dodge rating, is +1.96% dodge (1).

b) 307 shield block value (2)


Calculations
Given a 20% block chance, 55% total avoidance on a hypothetical tank, and a boss which hits for 20k attacking 100 times, with an attack frequency of 2 seconds:

a) Adding 1.96% dodge
An additional 1.96% boss attacks were avoided, totaling 39200 damage.

b) Adding the block value item and using Shield Block whenever possible (ie. 5 times), gives us:

- 50 seconds of Shield Block with 100% block chance where block value is 706 (calculated as 307 * 2.3, where 2.3 is the combined effect of the talent shield mastery, and shield block).
- 150 seconds with 20% block chance where block value is 400 (calculated as 307 * 1.3, where 1.3 is the talent shield mastery).

Under the 50 seconds of Shield Block, 11.25 attacks are blocked. Total damage mitigated is 12619 (calculated as follows: 706 *1.3 *11.25, where 1.3 stands for the effect of critical block).

During the remaining 150 seconds, 15 attacks are blocked, resulting in 7800 damage mitigated (calculated as follows: 15 * 1.3 * 400, where 1.3 stands for the effect of critical block).


Summary
In this example, dodge rating is nearly twice as good when it comes to reducing incoming damage, compared to block from items. That is even on a tank which already has a considerable amount of dodge and is thus subject to corresponding diminishing returns.

20% passive block and Shield Block mitigated a total of 20419 damage due to an item with 307 block value.
The same item, but with 100 dodge rating instead, led to avoiding 39200 damage.

References
(1) Satrina's explanation about diminishing returns (http://www.tankspot.com/forums/f63/40003-diminishing-returns-avoidance.html)
(2) using numbers on Wowwiki's explanation on statmods (http://www.wowwiki.com/Item_level) and doubling them to account for the 3.2 patch changes

Comments
While this must be considered a poor comparison for several reasons, one being that real tank stats were not used (which means that a warrior with 500 dodge rating like in this example, probably has more avoidance than the 55% I was using), dodge would presumably turn out to be even better.
Furthermore, it has to be considered that shield block value also serves the purpose of increase damage and threat, while dodge does not.
Regardless, I hope that this post was informative to the interested reader.

[Warloco]

A few comments:
1] A warrior with "400 dodge" will also have dodge from defense and agility, meaning the DR will be higher than what you suggest. On my warrior I have 392 dodge, 540 def and 135 agi- and yet 100 dodge rating converts to only 1.83% dodge.

2] I don't see the budget cost of dodge rating on that page. What I do see however is the budget cost of defense. For 1 block value I need to spend 0.65 item budget, for 1 defense rating I need to spend 1.2 item budget. In 3.2 the block would cost 0.325 item budget.

Now as I said, I dont know the cost of dodge since it goes without mention on that page. Instead I'll use the value of defense, as gems and gear seems to suggest they cost atleast roughly the same.

To get 100 def I need to spend 120 item budget. For that 120 item budget, I could get 369 block value.

Now then if I take your results and calculate them according to those values, I get:
Dodge: 39200/1.96*1.83=36600
Block: 20419/307*369=24543

By all means though, correct me if/where I'm wrong. Also my warrior is just about naxx geared, your 55% avoidance warrior will most likely get hit by DR more heavily than my warrior.

[edit] Perhaps it's worth while comparing to parry aswell:
On *my* warrior (Naxx geared), 100 parry gives me 1.34% avoidance. 1.34% avoidance would have reduced my damage taken by 26800. Any Ulduar geared warrior probably has more parry than me, and in terms of item budget block value might actually be more beneficial than parry rating after adding the DR an ulduar tank would be at.

[Stengel]

By all means though, correct me if/where I'm wrong. Dodge rating is included as "combat rating" on wowwiki.

Also, defense rating costs the same as dodge rating, not more.

See these two trinkets of the same ilvl and quality: Repelling Charge - Item - World of Warcraft (http://www.wowhead.com/?item=39292) and Valor Medal of the First War - Item - World of Warcraft (http://www.wowhead.com/?item=40683)

[Forklift]

I think comparing avoidance and SBV, while interesting and necessary, got you results that weren't terribly surprising. They're stats that aren't really substitutes. The main purpose of the former is not to reduce total damage taken during a 3min period of time, but rather to reduce the chance of an X-long string of hits. In my current setup, fully raid buffed, I have 58.5% avoidance, which means the chance of getting a string of two more hits immediately after any hit is 17.22%, and of three (making it 4 straight) 7.15%. One percent additional avoidance brings the chance of 3 straight hits down to 16.4%, and of four, 6.64%. If I literally gear for max avoidance, I think I can reach something like 67% avoidance, which brings this probabilities down to 10.86% and 3.58%. You can add in block rating, to calculate chances of strings of only unblocked hits, or strings of X number of unblocked and the rest blocked, etc., etc. The point is, avoidance is there to reduce the chance of getting RNG fucked and gibbed while your healers are running out of sunbeams, or getting silenced by Yogg, or whatever.

So usually I compare avoidance to straight stam or armor, plugging in boss hit values to see how many hits I could take without getting any heals except hot ticks, and the chances of getting gibbed after each hit. Stam (or armor, on physical hits) is obviously much better against slow, hard hitting bosses, because you're going to take 2- and 3-hit strings no matter what your avoidance level, given the 3.0 game mechanics, and so you just need to survive them. On bosses with quicker swing timers and more moderate hits, avoidance might win because pushing strings of 5 hits off the "realistic occurrances" table could actually really help your survivability.

SBV I don't even look at currently as a mitigation stat, at all. Even with the buff, it's too unreliable to itemize towards. SBV has to be paired with SBR (or potentially the datamined t9 4-piece that lowers shield block cd to 20s) to really count towards something. I think you could do a pretty interesting and useful comparison between avoidance and SBV, but you'd have to abandon this "total damage mitigated over 200 seconds" model and look at it more from a "chance of getting F'd in the A" model, since healer mana is rarely the problem in 3.0, and despite successive nerfs to regen, doesn't seem like it will ever be; rather, healer movement and surviving those few seconds of not getting direct heals is the key.

Edit: I think one potential way of doing it is saying alright, I'm going to be happy if I don't eat a string of unavoided, unblocked hits. You start from the other end--take 3000 SBV as a given (or some reasonable number assuming you gear somewhat towards it), and find out at what avoidance levels SBR becomes more valuable than avoidance. This is the point at which you can actually gear for SBR--which means if reaching this point is unreasonable, getting 3000 SBV is useless, as avoidance is better.

[Stengel]

I think comparing avoidance and SBV, while interesting and necessary, got you results that weren't terribly surprising.

Well to me it was actually surprising, SBV turned out to be somewhat better than expected after accounting for Shield Block.


I think you could do a pretty interesting and useful comparison between avoidance and SBV, but you'd have to abandon this "total damage mitigated over 200 seconds" model and look at it more from a "chance of getting F'd in the A" mode

How would you suggest doing this exactly?

[Forklift]

Start here: http://www.tankspot.com/forums/f200/37241-power-avoidance-preliminary-results.html

[Gnarg]

I must say I like these numbers. Remember, pala's and warriors have strong abilities tied into block, namely holy shield and shield block. With T9 having shield block on a 20 sec cooldown will be INSANE, with block values going around 3k with strength buffs (guestimate), and being hit by a hard hitting boss (25k), you can FORCE 20% damage reduction when you need it. This will be very strong.

I think shield block will now be used much more as an actual melee damage reduction abilities instead of just for boosting shield slam.

For paladins block value will be pretty sweet as well, they can keep 100% up all the time, so it will be much like armor for them. Using your numbers, 307 block value is 1,22% of a 25k hit, which is pretty close to the 1,96% you are getting from dodge. And for a paladin this will be gauranteed mitigation (with HS up), not relying on RNG like dodge does. It will actually outshine dodge for them for damage mitigation with mobs hitting for less than 15,7k. This means it will be THE off tank stat, since there are many mobs that hit for less than that tanked by off tanks.

I don't think we'll be stacking block soon but it at least won't be like now where block value is almost an ignored stat on gear.

Block rating is still pretty bad though imo, especially for paladins cause it's so easy for them to get unhittable.

[Martie]

3k block would indeed be nice.
Nice, and unrealistic to expect.

You do have a point about the paladins, they do indeed gain a nice boost from the heightened block value... except that so much block value is paired with block rating (which is damn near useless.)

[Gnarg]

Yes when I think about it 3k might be way too high. Think that in ulduar gear if you focus purely on block you can get to around 1,8k (Really dunno, never made a block value set). Think 2,5k in T9 gear wouldn't be unrealistic.

Ah well it's only speculation until we see more of the new gear.

I'd love to see 10k critical blocks tbh :D.

However, fact is still that you shouldn't just calculate the mitigation of block value by simulating pressing shield block every time the CD is up. With the higher block value and 20 second cooldown, it can be pretty damn sweet for every time you get hit to the 30-40% area of your hp bar or you know some movement is happening.