Critical Block < onlyinclude > < / onlyinclude > What is Critical Block . Critical Block gives a percentage chance to double the damage reduction provided by your block . When shields are being used , there are two separate calculations — the block percentage and the damage reduction . First , there is a calculation to see if a block occurs ( similar to a parry / dodge ) . If a block occurs , then a separate calculation determines how much damage is reduced . Critical Block increases the damage reduction by 30 % , that is the blocked amount is 60 % . Shield using protection classes have as their mastery , Critical Block . They have a base amount of block , and block obtained from mastery . 179 mastery rating gives a Protection Warrior 1 point of mastery that increases both their block rate and critical block rate by 1 . 5 % . Block still only applies to physical damage . The critical block rate is 8 ( the base amount ) X 1 . 5 plus Mastery / 179 X 1 . 5 . Mastery here is the mastery shown on the Armory . It appears then that critical block starts out at 12 % and block starts out at 32 % . Ignoring the Hold the Line talent , one may be able to look at their block chance , and subtract 20 % from it to determine their critical block chance . The Avoidance Cap was 102 . 4 % , when your cumulative Dodge , Parry and Block + 5 % Boss miss reach 102 . 4 . P . S . Avoidance ( avoid getting hit , similar to dodge ) and Mitigation ( reduce hit damage , similar to parry ) are two separate things . Do NOT confuse them . Heroic geared protection warriors in Cataclysm were sometimes able to block cap . Their normal block rate could be 52 % which is combined with their Dodge and Parry , say both at 14 % , giving them an 85 % chance to block , dodge , parry an attack , or the boss miss them . Combine these stats with their use of Shield Block , and their number was pushed to 110 % , above the diminishing returns cap of 102 . 4 % . Shield Block increased their block chance by 25 % for 10 seconds , and had a 30 second cooldown . The above warrior would at at a minimum , block 30 % of incoming physical damage with shield block active . Shield Block was a significant cooldown option for them . It could also be used on every cooldown , if it was not needed for spike damage . Shield block and critical block . Assume a Warrior blocking 60 % of attacks . And that they have Dodge of 14 . 4 % and Parry of 15 % . Their CTC ( Combat Table Coverage ) is 60 . 0 + 14 . 4 + 15 . 0 + 5 . 0 or 94 . 4 % which is 8 % short of full CTC . Critical block would be 40 % . Using shield block pushed critical block to 40 % plus the excess of ( 25 % - 8 % ) which is 57 % . This 57 % was the critical block chance . The blocks would be some 30 % and some 60 % . 30 % X 43 % plus 60 % X 57 % is 47 . 1 % . The average amount blocked . What mastery does for a Protection Warrior . Adding mastery when one can only block cap using shield block does this : It increases normal blocks and critical blocks . Critical blocks are less frequent than normal blocks , but significant . The warrior still takes unmitigated hits when shield block is down , but takes less of them , reducing total damage taken . When the warrior shield blocks and is now above the 102 . 4 block cap , he pushes unmitigated hits off the table . The more mastery he has , the greater the benefit of shield block . Excess mitigation above the 102 . 4 diminishing returns cap , is converted to critical block chance . The 60 % of damage blocked value , might be said to have exponential growth . So the same mastery benefits the warrior with or without shield block , and the more one has , the more effective shield block becomes . Mastery or shield block percentages for the above warrior are not subject to diminishing returns . Dodge and Parry are . If one is trying to reach the ' using shield block - block cap ' as easily as possible , Mastery is more efficient at that giving roughly 50 % more gain than Dodge or Parry . At the same time , it is increasing critical blocks , which also helps in making the choice between mastery and other attributes . Increasing critical blocks might be thought of as raising the average blocked amount . Moving its average from 30 % towards 60 % . Warriors have a 12 % base amount of critical block . Mastery adds to that at a rate of : mastery / 179 = the additional critical block . So adding mastery does at least 2 things , more blocks , and bigger blocks . Say a new level 85 warrior is just at the block cap threshold , 77 . 4 % . ( 102 . 4 - 25 . 0 ) . They use shield block , and are at least blocking 30 % of damage , with a few critical blocks . Let ' s say they now add 5 % to their block rate reforging to more mastery . They are blocking more and their blocks on average are bigger . When they shield block , that 5 % from mastery is now 10 % increased critical blocks . This is because when they took their 5 % from mastery reforging it added to their critical block rate too . When they shield block now , that 5 % they took is now excess mitigation as well . It is added to their critical block rate again . One may argue that from the threshold on , they are getting double benefits to the blocked amount . This explains at least part of the exponential growth mentioned elsewhere on this page . Raising the average blocked amount ( from 30 % towards 60 % ) seems significant , and warriors currently have a 2 for 1 way of doing that , at certain gear levels . How much mastery would be too much ? When the warrior is asked to generate more threat and needs expertise and hit . During magic damage fights . In those situations , the warrior may have too much mastery . The mastery cap may be at 102 . 4 % without shield block . It may be when shield block means all blocks are critical blocks . It is noted that , the damage reduction of a block is . 7x . The damage reduction of a critical block is . 4x . There is a greater percentage difference between . 7x and . 4x than between 1 . 0x and . 7x . What is this critical block cap ? For a warrior , 67 % block , 15 % dodge , 15 . 5 % parry , and the 5 % boss miss brings one to the block cap . Subtract 18 % of that , the difference between base block and base critical block . You get 49 % critical blocks . If it is true that additional mastery adds to both excess caused critical blocks and critical blocks , one can bridge the gap two for one from 49 % to 100 % . Another 25 % block would about do that . Adding 67 % and 25 % for 92 % would bring one to the critical block cap , without procs . Adding 92 % block , 15 % dodge , 15 . 5 parry , and 5 % gives us : 126 . 5 % . This may be close to the critical block cap for Warriors . Entry level Firelands tanks may have around 87 % combined block / dodge / parry / boss miss . There are many factors to consider . The particular fight or the raid make up . As usual , the tank is advised to be as adaptable as possible . Comparing Block to Dodge finds that a block generates rage , while a dodge does not . In some fights rage may be an issue . Gearing a block tank . Mastery is highly valued . The Hellscream ' s reach trinket a good idea with their high amounts of mastery . The magic resistance one , and the on demand agility one . Parry and Dodge proc trinkets seem to work with the block cap . Combined with a shield block , they can push you significantly past the block cap , perhaps picking up critical blocks during their use . Most tanking armor has 2 of 5 stats . Dodge , Parry , Mastery , Expertise , and Hit . You may favor armor that has Mastery and either Dodge or Parry . While hit and expertise are valuable , if survival is your highest priority , the block cap is perhaps the best way to do that . According to theckhd , 1 mastery rating ~ 7 armor for damage reduction . 1 avoidance rating ~ 6 . 5 armor for damage reduction at projected avoidance levels for T11 . Reforging and Critical Block . The current thinking on the EJ forums seems to be Mastery > Parry > Dodge for survival . Mastery is taken when possible . Some balance between Dodge and Parry may be good , as both are subject to diminishing returns . Parry is favored a bit over Dodge because of the Hold the Line talent , and the increased damage a Parry provides . Hit and Expertise can be given up if survival is the goal . Current Issues . A number of warrior tanks have switched to the block meta gem away from the increased armor meta . Some spreadsheet scenarios support this .