An Ex-Gnome Tank's World

On Block Rating

June 6th, 2008 Posted in Theorycrafting

A recent discussion I had with our raid leader over block rating brought some useful information to the fore. It started with him suggesting that my passive block chance was low and I should perhaps tweak my gear to increase it (this was as a result of a parry-accelerated crushing blow causing a wipe the night before).

It’s well known that to avoid crushing blows entirely, the sum of miss, dodge, parry and block percentages must be greater than 102.4%. It’s also well known that bosses which can crush, have a 15% crush rate, and that if an attack is blocked, it cannot be a crushing blow.

However, what’s not widely understood is what passive block rating does to the chance you will be crushed. And the answer is this: nothing at all. That’s not quite true, but the chances of being crushed remain the same until you reach greater than 87.4% miss, dodge, parry and block.

Let’s work through some examples, and assume a warrior has 25% dodge, 20% parry, 20% block and a 10% chance to be missed. He will also not be using shield block. I’m going to simplify things somewhat by ignoring the extra 2.4% you’d need against bosses, and assuming that the goal is 100% rather than 102.4%.

So, in 100 attacks:

  • 10 will miss him
  • 25 will be dodged
  • 20 will be parried
  • 20 will hit and be blocked
  • 10 will hit and not be blocked
  • 15 will hit and crush

So, let’s add some more passive block to the warrior, and let’s see how much this changes things. He now has 30% block, but all the other stats remain the same. So we have our 100 attacks again:

  • 10 will miss him
  • 25 will be dodged
  • 20 will be parried
  • 30 will hit and be blocked
  • 15 will hit and crush

What we see is that the same number of crushing blows will land. The only difference is in how many hits we block (and the damage reduction from that). We need at least 31% block before we see any reduction in the number of incoming crushing blows.

So for raid bosses who will typically hit for 6-7k, your block is merely reducing the amount of damage taken from normal hits by maybe 500 damage. Useful but not that useful. Yes, the 500 points might save you, but if your healers are awake it’s not going to help that much.

Of course, in other circumstances block rating is desirable, such as when AoE tanking with a shield spike. The rest of the time, it doesn’t make enough difference to be worth stacking. It’s an all-or-nothing stat.

  1. 4 Responses to “On Block Rating”

  2. By Tankette on Jun 6, 2008

    That was a good explanation. I haven’t spent much time looking at my dodge/parry/block but I know I am far from passive uncrushable.

  3. By Dezdemone on Jun 6, 2008

    YAY! I am not the only one who thinks block rating sucks!! I hear from soo many people who confuse block rating with block value… =)

  4. By sundermonkey on Jun 12, 2008

    feel free to correct me if im wrong here but i always thought the only real value in block rating is for a passive unchrushable set.

    to put it this way, if you have 102.4% avoidance without block rating, you get no rage. you take no damage. you take it in the pooper.

    where as if you have 102.4% with a solid chunk of block rating you will block all the attacks that hit and you wont get any chrushes.

    on a side note if you only had 90% avoidance then all that landed would be crushes?

  5. By Nam on Jun 12, 2008

    Yes, you’re right in what you’ve said so far.

    In terms of bosses, the only time it’s useful is in a passive uncrushable set. And the only really useful passive uncrushable sets involve mostly Black Temple and Sunwell gear.

    However… if you’re tanking lots of mobs on a trash pull (and especially if you have a shield spike or similar) then block rating will reduce incoming damage considerably. That’s about its only use.

    As to 90% avoidance, yes. Due to the way the combat table works (it’s a single roll system, EJ can tell you more if you care), the 10% of hits that land will crush.

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