I suspect its yet another druid bug.
Has anyone successfully got poly curse dagger to work while in wolf or bear form?
The deception and corrosive salt parts proc however, the curse vector part doesn't seem to work. I've not had a single curse, blindness, exhaustion or energy drain effect proc. (tested by killing about 200 mobs in the vale) Hardly surprising though it did manage to curse me a few times during testing. (no bloody surprise the negative part works)
I tried un equipping and re equipping the weapon a few times just to make sure its not one of the other druid bugs were some items don't work unless you swap them in and out.
I then tested with my rogue who also has a poly curse dagger and at least one effect seemed to proc about every other mob (sometimes more than one effect)