Primary

 Intelligence
 Strength
 Agility

Damage

 Physical Damage
 Elemental Damage
 Melee Damage
 Ranged Damage
 Fire Damage
 Ice Damage
 Light Damage
 Critical Damage
 Armor Penetration

Defensive

 Health
 Mana
 Armor
 Resistance
 Dodge
 Tenacity
 Life Steal
 Mana Steal
 Spell Vamp

Miscellaneous

 Move Speed
 Attack Speed
 Projectile Speed
 Cast Rate
 Jump Force
 Range
 Melee Range

Resistance

Resistance defends against  Elemental Damage, making it useful against Classes such as the Mage, Priest, and Warlock. Resistance also increases as  Intelligence increases. Resistance covers for all forms of  Elemental Damage, including  Fire Damage,  Ice Damage, and  Light Damage.

Resistance is not as effective for targets which deal mostly  Physical Damage, that will require  Armor instead. Resistance is countered by Resistance Penetration.