FYI, there is a thread on both the PTR forum and the mmo-c forum right now discussing how this helmet doesn't work on raid/dungeon bosses (or probably anything CC immune). The helm proc requires them to get the debuff that slows, not just be taking damage. To me this seems like a textbook case simple oversight. Sephuz is specifically designed as the cc proc'ing legendary, I really doubt the helm was meant to be another, for such a small gain anyway.
Trying to get attention straight to the devs via Twitter might be called for.
