Base Stats:
Strength - Increases attack power with melee weapons
- Warriors, druids in feral forms and paladins gain 2 attack power per 1 strength.
- Rogues, hunters, shamans and other classes to whom strength is less important: 1ATP per 1STR
- Strength DOES NOT increase critical strike chances and DOES NOT improve chance to block.
- Also there is evidently something screwed up about strength contributing to block value on WoC.
What does this mean for my class?
- Warriors, druids and paladins are the classes that truly benefit from STR other classes should consider other stats.

( Please keep in mind that for DPS classes HIT rating is primary to all other stats, otherwise you're useless. )

Agility
- Increases attack power with ranged weapons or melee weapons for some classes.
- Crit based on agility varies from class to class.

AGI per 1% crit:
Druid: 25 AGI
Hunter: 40 AGI
Paladin: 25 AGI
Rogue: 40 AGI
Shaman: 40 AGI
Warrior: 33 AGI

( Any Class not listed should not even consider gear with agility)

- Increases armor by 2 per point
- Increases Chance to Dodge attacks
- What classes should stack Agility?
- rogues & hunters
- What does this mean for my class?
- Paladins should take AGI as secondary to straight crit and haste
- Tanking Feral Druids should stack stam and straight dode rating after hitting def. cap then AGI
- Enhance Shamans should stack straight Attack Power & Crit before AGI
- Tanking Warriors should stack Stamina, defense rating, armor and mitigation stats (block, dodge and parry)
- DPS warriors should stack Strength and straight crit, then agility, but should you decide to spec fury, be aware that
it requires more hit rating than arms.
( Please keep in mind that for DPS classes HIT rating is primary to all other stats, otherwise you're useless. )

Stamina
- A fairly obvious stat. Stam = HP
- After your first 20 points of stamina, every 1 Stam will grant 10 health to the player and the player's pet.
- Stam generally comes on every piece of gear and is important if you want to live.
- Tanking classes should stack Stamina.

Intellect
- The first question you should ask yourself in looking at gear with +intellect is "Do I have a blue bar on my nameplate?"
If your response is no, the gear probably isn't made for you.
If your response is yes, please keep reading to see what INT can do for you!

- INT increases how much mana you have. Every 1 point of INT after the first 20 increases your mana pool by 15 points.
- INT increases chances for critical strike with your spells.
- INT increases the amount of mana you regenerate every 5 seconds (MP5) by Spirit.
- Critical Spell Strike based on INT varies from class to class:

INT per 1% crit:
Warlock: 81.92 INT
Druid: 80 INT
Shaman: 80 INT
Mage: 80 INT
Priest: 80 INT
Paladin: 80.05 INT

- Intellect is secondary to straight Spell Critical Strike Rating for casting classes, however you're also useless with no mana. =)

( Please keep in mind that for DPS classes HIT rating is primary to all other stats, otherwise you're useless. )

Spirit
- Spirit increases mana and health regeneration.
- Health generation from spirit is not active during combat.
- Mana regen is active in combat, however the *5 second rule* applies.
- 5 seconds after a spell cast mana regen will not happen, however some classes have talents that make up for this.
- INT increases Mana per 5 seconds (MP5) generated by Spirit.
- This stat is mostly useless to everyone save HOLY priests and RESTORATION druids.
- Warlocks may stack some spirit (but do not much!) for Fel Armor.

Added (2009-07-16, 1:18 Pm)
---------------------------------------------
Melee Stats:
Weapon damage - Comes from the player's weapon. Increased by enchants or other altercations, such as sharpening stones. Scopes, ammor or arrows for ranged.

Speed - Weapon speed comes from the players weapon. This determines the amount of time between attacks. Please see specific classes to determine what weapon speed is best for you!

Power - Attack Power, Increase damage of your weapon. Increased by gear and buffs with ATP and indirectly by Strength and agility. Please see those stats to find which is best for you.

Hit Rating - Increases your chance to hit with a melee weapon. Incrased by hit and combat rating.

Crit Chance - % of attacks that will critically strike. Increased by critical strike and combat rating and indirectly by agility.

Expertise - Reduces the enemy's chance to parry or dodge by .25% per point of expertise.

Armor penetration - Reduces the target's armor.

Spell Stats:
Bonus Damage - Increases the effect of damaging spells. The exact amount added varies with the spell's cast time or duration. Bonus damage can also apply to specific spell schools such as shadow/holy/fire/frost/nature etc.

Bonus Healing - Increases the effect of healing spells.

Spell Hit Rating - Increases the chances that spells will hit their target. Stat is not needed for healers, heals don't miss. (i.e. it's always a bad excuse)

Crit Chance - % of attacks that will critically strike. Increased directly by Spell Critical strike rating and indirectly by intellect.

Haste Rating - Decreases spell cast time. Increased by haste rating.

Mana Regen - MP5 - the amount of mana restored every 5 seconds. Increased by direct Mp5 and indirectly by spirit.

Defensive Stats:

Dodge - Increases chance to Dodge melee attacks. Ranged attacks cannot be dodged. Increased by Dodge rating and indirectly by agility.

Parry - Chance to block melee and ranged attacks with your weapon. Ranged attacks cannot be parried. Increased by Parry Rating.

Block - Chance to block melee and ranged with a shield. Increased by Block rating.

Block Value - Damage blocked by a shield. Listed directly on the shield and increased by other gear.

Defense - Increases...defense? Increased by Defense rating.

Armor - Decreases physical damage received. Increases your pet's armor.

Resistances - Decreases damage from certain magical schools - only needed when told so for boss strategies.

Resilience - Decreases chances to be Crit and reduces damage
inflicted by DoTs (damage over time). Increased by resilience gear.
NOT NEEDED FOR RAIDING. This stat is built for PvP. Tanks may use it to reach certain caps.

Health regeneration - Rate at which health is restored. HP5 - increased slightly by spirit.

Added (2009-07-16, 1:19 Pm)
---------------------------------------------
Rogue: 20 AGI = 1% Dodge
Druid: 14.7 AGI = 1% Dodge
_________
INT increases MP5 indirectly through Spirit.

_________
These would all vary based on which tanking class you are refering to. =)
for a paladin it was 102% Including holy shield for "block cap"
For warriors it's 75% so stacking stam is much easier.
For a druid you should try to have a minimum 415 Defense, around 20k armor, 30% dodge though as you gear you can get MUCH higher.
_______________
As for the ability to survive on only stam and armor, only druids could do it and only due to the raw mitigation of bear form. It is obviously NOT recommended.
_________________

Rogues & Druids in Kitty form: 40 Agility would round out to 40 ATP
Druids in Bear form to not benefit from agility in the same way.