I had it on for a boss last night, but unfortunately I didn't have enough buff slots on my target active. I'll let you know next time I use it on a boss level mob, as we should have our members with WWS back.
Edit: Actually, I forgot our dps warrior runs WWS. So I've got a list of the attempts. Over 10 tries, it procced 12 times. Once I believe was a trash mob.
One one try, it procced 5 times, and on half attempts, it didnt proc at all.
The debuff itself has a 45 second duriation. Seemed to proc about once every 1 and a half minutes according to this WWS report, which would indicate that its not getting to the point where its stacking.
Note that I wasn't capped in Axe skill by the point, and my guildies WWS isn't quite as reliable as our guildie that usually does it. So I'll test it out a little more, and get you an answer with more depth when I can.
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"Good tankadins know all the fundamental rules of tanking
Great tankadins know when to break these rules" -Passionario