I had some issues with Huntress too, namely the ending, which seemed too rushed and too many things left unresolved (maybe there will be a sequel to Huntress?) and that the Chinese-ness faded away as the story went on.

Sequel to Moonshine, yes! Or even just more stories with different characters set in that world!

The Merlin Conspiracy was the first DWJ book I read, years ago; I remember liking it -- at least enough to seek out other books by her -- but none of the details/issues you point out. I'm not sure if I should re-read it or not.