I tried it in the Bloodtide Coast mission, which was under the Jormag category (which, I'm assuming is an icebrood one), and I tried to use it several times at point blank range on that last boss when the breakbar was down, and nothing happened.
I've already successfully done the Primordus staff one.
Any thoughts? Maybe a different mission/boss?
In the event I don't get a chance, thank you all for the company and help when I needed it from time to time.