NQ mobs are stunnable (even by Violent Flourish). The
boss can be stunned by a Black Mage and slow/para'd, but I didn't try with Violent flourish. He takes reduced damage overall. I see a 1251 Blizzard V in the logs, and two 2150~60 Bliz Vs against the Aerns, and 30~50 damage crits, 15~25 damage normal hits with Dia III and meat and Minuet V, which is about half what the Aerns were taking or a bit under.
Mobs harder than any limbus zone other than Apollyon CS. They're about as hard as killing level 90 mobs, assuming those mobs can 2-hour, reraise, and you're dealing with 2~5 at once.