Well On C-West i had the Gabs blessing and that shit goes off alot. But i always had more then like 3 ppl attking me at the same time. In Vs's the most it ever went off was 3 times.
Im sure its for each attack cause the more you think about the more u will realize how much those Skill options will help. Pay attention to it and use em to your advantage and they will be the diffrence between dieing and staying alive. Id have to say that Windforce bow at +7 is better then using an IB +8. but if you get your hands on a +9 Iron bow id still want the windforce for certain situations. All Classes have diffrent weapon choices and good players dont just stick to one. Id prefer the Windforce in close combat situations rather then an IronBow.