I have a newer perspective now with each character. One of the things that helped me was to sit and redefine what each POV character's goal was. I already know their respective overall plots and what they want to achieve, but I wanted to really highlight what was the most critical thing for each to either accomplish or prevent at this point early in the story.*
What is driving each character right now?
For the duke it is simple: He will do anything to ensure his family keeps their throne.
For the squire it is simple: The lord of the Isle (the duke's brother) has charged him with one single purpose: keep the crown prince alive.
For the duke's daughter, I'm still working on it. The most important thing to her is her diplomatic mission to secure a peace between her family and the outside threat. Unfortunately for her, she has been sent on this mission without a critical piece of information that will undermine all of her efforts. After this, her driving force will be finding a way back home, escaping the diplomatic prison she will find herself.
So, even though these characters are in the same situation they have been since I started writing this version of this story, by sharply defining their single most critical tasks, I think it will add more tension to the story. It will help drive the actions of these 3 characters and influence some consequence-filled choices they will be forced to make.
I think one of the problems I was having was these 3 weren't as afraid of failing at these tasks as they should be. I wasn't raising the stakes on them enough. They weren't feeling the pressure, weren't recognizing the enormity of their challenges.
As I add in some new scenes to fill out the opening section and weave in the beginnings of the overall unexpected mystery element I think the tension and excitement level of the WIP will be enhanced to where it needs to be. And I'm already feeling better about capturing the proper narrative voice for each POV character.
High stakes pressure and how each reacts to it will help capture their personalities best.
*My thanks to Holly Lisle and her free module developed for her How To Think Sideways seminar for pointing me in the right direction.