Getting more than 5% haste from buff

[Aszala 0]

So basically i'm getting about 5.5% haste from the haste buff and I have no idea how/why. Has anyone experienced this and can shed some light on why this is the case?

 

http://i.imgur.com/Qfz35QD.jpg

[Grognard 6]

It works weird. If I remember right, it adds a flat 5% then adds an extra 5% of your rating from gear. That's why the first haste plateau (15%) is at ~9.5% on sheet rather than 10%.