Note that the mitigation formulas are with a paladin in mind.  I believe that warriors have the same but Druids I know are slightly different.

Spell Damage: Made for arcane spec. mages.  Specifically for arcane missile spamming.

Mitigation: Assumes 490 defense already.

Stamina: score is based on socketing everything with +12 stamina gems and the meta socket with a +18 stam gem.  The score should equal the maximum stamina that item can give you. 

Mitigation without Blocking: Use for searching for the best 100% mitigation items. 

Armor: Gives item score based on armor value.