It's a good way to keep people guessing, and I love hearing Adam describe things unique to the setting. It looks like there was at least a little added to it past though. Between what sounded like the addition of yuan-ti spellcasting and the change to the black dragon's multiattack (normally they make one bite and two slightly weaker claw attacks, not three bites) means that on paper, Zuduo was even more of a challenge.
That said, it didn't feel like Adam was playing Zuduo maliciously, if that makes sense. Dragon fights are no joke, but Berg could have been killed outright more than once if she didn't have that creepy, vaguely nurturing reaction to his "dead" body. I kind of want to know more about what her deal was now, even if the valley has a new evil snek priestess.