Each point of +Defense skill adds 0.04% to the chance to be Missed, to Block, to Dodge and to Parry.
This means +25 Defense will grant you an extra 1% Miss, Parry, Dodge, and Block. The formula is constant across all classes.
- Critical Hit immunity for a level 80 player against a raid boss occurs at 540 Defense and requires a defense skill of 140 (689 +def rating) from gear to achieve. The defense minimum for heroic dungeons is 535 Defense.
- Critical Hit immunity for a level 80 player against a raid boss can also be achieved by a Resilience of 5.6% and requires a resilience rating of 459.2 to achieve.