One time in Unicorn Way, I was battling Rattlebones with my ice wizard and I used the Freeze spell to stun him but... apparently, after when the stun block was activated and it was Rattlebone's turn, he still attacked! The exact same thing happened with Lady Blackhope when I casted the Freeze spell on her too! All that happened was the stun animation and the stun block being triggered, but no freezing(stunning). I don't know if this is happening to other wizards with the stunning spells, but only the bosses in particular and not the "ordinary" bunch of enemies without the boss rank. I'm not even sure if this is a glitch or the new skill that the bosses of Spiral has learned. :? If you ask me, this event only happened once with those two bosses.
Yeah, apparently stun spells no longer work. At first I though Bosses were immune to stuns now, but since I have noticed that many regular enemies are also immune. I finally took all stuns out of my decks because they were useless.