Trouvé sur les forums officiels de WoW:
[quote]Q: How does the off-hand damage penalty work? How is it affected by the dual wield spec talent?
A: The off-hand normally just does 50% of what it normally would do. So:
(Weapon DPS + Attack Power DPS Bonus) * 0.5
WIth the dual wield spec 5/5, the off-hand does 75% damage, so just subtitute 0.75 for 0.5.
The tooltip for the off-hand was previously bugged, causing numbers which did not make sense. If you had the talent, a weapon would be listed as doing more damage in your off-hand than in your main. Some data posted prior to the tooltip fix suggested that the tooltip was bugged. The change to the tooltip seems to confirm this.[/quote]
Le DPS de ton arme secondaire est bien réduite de 50%. Tu peux le monter à 75% via l’arbre des talents si tu es un rogue. Les autres classes je ne sais pas 
Il y a aussi un autre paragraphe intéressant:
[quote]Q: How does the attack power bonus work? Why is a slow weapon better in the main hand?
A: The attack power bonus is a pure DPS bonus. Roughly 14 points in attack power equals 1 point of DPS bonus…I don’t believe it scales by level.
Since it is a DPS bonus, and not a damage bonus, it works in an interesting way. Suppose you have a 20 dps attack power bonus, so roughly 300 attack power. For argument’s sake, lets suppose you have a main-hand weapon which is 1.00 speed with an average damage of 20. For this weapon, 20 dps means 20 damage per per hit. So your average damage in your main hand will go up 20 damage points due to the attack power bonus.
Weapon #1:
20 average damage, 1.00 speed = 20 dps
+20 average damage = 40 average damage, 40 dps
Now let’s say you have another weapon which is 20 dps, but 2.00 speed. So, it’s average damage per swing is 40. For this particular weapon, 20 dps = 40 damage per hit. So in this case, your average damage will go up 40 damage points due to your attack power bonus.
Weapon #2:
40 average damage, 2.00 speed = 20 dps
+40 average damage = 80 average damage, 40 dps.
Both weapon #1 and #2 have the same DPS, but weapon #2 is a much better mainhand weapon. Obviously there are no 1.00 speed weapons, but the point still holds.
All this explains why, for instance, the Toxic Revenger ends up having a slightly higher damage range than the Black Menace. Black Menace has an average damage of 44.5 @ 1.5s. Toxic Revenger, on the other hand, has an average damage of 39 @ 1.9s. The Black Menace has a much higher DPS, but since the average damages are so close, you’ll notice that your tooltip damage range will be slightly higher with the Revenger, assuming you have a reasonable attack power.
This raises a very interesting dilemma when choosing a main-hand weapon. How much DPS are you willing to give up on the weapon for a higher damage range?[/quote]
Cela nous dit que pour deux armes à DPS équivalent, l’arme la plus lente dans la main principale est préférable quand on est ambidextre. Je n’ai pas bien saisi quel est ce « attack power bonus ». Est ce propre à toutes les armes ou est-ce un bonus inhérent à certaines seulement?