Originally Posted by Malan

I like the idea of using that image Yo, but it may be confusing to some people. When examining the graph, combos such as a 3.0/1.0 are in the same region as the 3.0/3.0 combo. Maybe its the scale of the graph - if you were to isolate the ranges of weapons that we're really interested in here (2.8 - 1.4) maybe it would show the effect more clearly?

Originally Posted by Nisall

The problem lies in the fact that both hands proc the same event. The statement that implies that when dual wielding your proc rate is 36% is saying that there is a 36% chance one of your weapons will proc a windfury.

Just to simplify things;
WF1 = windfury (rank 5) proc from your mainhand
WF2 = windfury (rank 4) proc from your offhand
WF3 = windfury proc from either (doesn't differentiate between MH and OH procs)

various scenarios
-Only equipping a MH you would have a 20% chance to proc WF1
-Only equipping an OH you would have 20% chance to proc WF2
-Dualwielding, pre-WF rank change, your MH has a 20% chance to proc WF1 and your OH has a 20% to proc WF2
-Dualwielding, post-WF rank change, you have a 36% (0.8*0.8) chance to proc WF3

EDIT: Blizzard hasn't changed the proc rate for single vs dualwielding. The confusion just happens when people use the same word to mean different things. Sometimes "WF proc" is used for a specific hand which procs and sometimes "WF proc" refers to any proc that happens.