Shallan has been my least favorite of the main POV characters. Nevertheless, I didn't find myself seriously objecting to how heavily she was featured in this book. Maybe it was because she was typically in very interesting situations. Like for many readers, the split personality disorder thing was a bit grating for me. But somehow my overall perception of her improved during this book. I guess her split personality disorder doesn't bother me as much as her previous flood of irritating (to me) "humor".
In short I was fine with the balance, and I am not team Shallan. This book was just outstanding.
Personally, I need more Jasnah. She is my favorite character. I think she hasn't quite gotten her due so far.