Ultimate Guide to Stats and Attributes in World of Warcraft - Defensive Stat Breakdown

 Defense is a tanking stat designed to give tanks of all classes the things they need to avoid and survive physical hits. It has many functions. Each point of Defense skill (not rating) adds a .04% chance to be missed by the target, and to dodge, block, and parry - meaning for every 25 Defense skill you have you increase the miss rate of your opponent by 1% and give yourself a 1% each chance to dodge, block, and parry an incoming attack. At level 80, it takes 4.92 Defense Rating to make 1 Defense Skill.

Beyond that, Defense also reduces a tank's chance to be critically hit, and if he stacks enough Defense he can become totally uncrittable. At level 80 a Defense skill of 540 is required to eliminate your chance to be critically hit by any mob or raid boss. For Heroic level dungeons, a Defense skill of 535 is all that is needed. Raid bosses have a 5.6% chance to critically strike a level 80 player. Druids who take the Survival of the Fittest talent get a 6% chance to not be critically hit, making Bear Tanks naturally crit-immune.

Defense is found on Yellow Gems.

Dodge is one of the three avoidance mechanics in the game. Dodge Rating, usually expressed as a percentage, is your chance to dodge an incoming melee attack (do not confuse Dodging with Missing - they're unrelated). When a player dodges an incoming attack, the entire attack is avoided. Players cannot dodge attacks coming from behind them, but mobs can. Additionally, a player cannot dodge if they are stunned. Dodge percentages are derived from three things: Defense Skill, Dodge Rating, and Agility. As mentioned above, 1 Defense skill gives a 0.04% chance to dodge an attack, and the dodge derived from Agility is purely dependent on class, spec, and level.

 Dodge is a complex mechanic because it is subject to diminishing returns. This means that the higher your dodge chance gets, the more points of Dodge Rating you'll need to increase it further. That said, there are two kinds of Dodge - Diminished, and Undiminished. Undiminished Dodge doesn't trigger Diminishing Returns, and is therefore preferable. Undiminished Dodge is dodge from your class' base dodge chance, dodge from Talents (like Anticipation), and Dodge Derived from your base Agility. Dodge from Dodge Rating, Dodge derived from Agility from gear and buffs, and Dodge derived from Defense is all subject to Diminishing Returns.

Dodge is found on red gems.