I have two more encounters to play out (Kua-toa, duegar). Overall the difficulty feels the same to me, but less reliant on cheese strats. (Except for the Githyanki patrol, and the Beholder is still a lot easier with a battlemaster handy).
Zhalk is way easier with Shadowheart involved. I usually alternate attacking Zhalk and the mindflayer so when one dies the other is one attack from KO. I've been successful in 3/3 attempts at the fight.