The Windfury Cooldown
After windfury procs it cannot proc again on either hand for 3 seconds. Since no usable 1H weapons are slower than 2.9s (or 3.9s with flurry), this means that no 1H weapon in the entire game can proc windfury twice in a row. Note that this means that windfury will proc less than the 20% promised on its tooltip. Please read "Optimal Weapon Speeds" below for more information.
- When only one weapon has windfury, each hit outside of the cooldown has a 20% chance to proc WF. This leads to a 11-18% overall proc rate, depending on gear, weapon speed, spec, and luck. Slower is better.
- In version 2.0 the shared cooldown could be avoided by downranking windfury on the off-hand. This was removed in 2.1 and the cooldown is now shared. This change reduces overall enhancement shaman DPS by 10-18%, depending on spec, weapon speed, gear, and spell use.
- When both weapons have windfury of any rank, each hit outside of the cooldown has a 36% chance to proc windfury. This leads to a 11-14% procrate with weapons faster than 2.0s unhasted and a 14-18% procrate with weapons slower than 2.0s unhasted. Slower is better. Handy reference chart:
3.0s normal, 4.0s with flurry = no swings wasted (no 1H weapons >20dps exist at this speed)
1.5s normal, 2.0s with flurry = one swing wasted
<1.5s normal, <2.0s with flurry = two swings wasted
http://www.wowblues.com/eu/tbc-enhancement-shaman-faq-394130313.html