Cascading dropdowns works great except when it comes to people fields. It will automatically select the first person (when the field is set to multi-people).
As a work around, I have another field that converts it into a text field.
Do you ever see this being resolved with Cascading drop downs?
This solution has never been intended used with people pickers, but it might be possible to add this to a future release. Can you add an attachment with some screenshots so that I can see exactly what you experience?