Warrior · Fury · tier 4 · from level 25
Dual Wield Specialization
+14.6 Attack
5/5 · level 60 · per cast · with a one-handed weapon
Dual Wield Specialization
Rank 5/5
Increases the damage done by your off-hand weapon by 25% and the Rage generated by your off-hand attacks by 50%.
Averages, counting crits and misses, for a level 60 Warrior with a typical weapon and no other gear or buffs, against a target your level. Worked out from the game's own data, the same way as the Foresight addon.