1) There is a small Diablo 3 reference in the second book of the "Journey to Wudang" series where the main character goes to meet the Archivist (who is a big fan of Diablo 2). Of course the Archivist is an elite ghost in Act 2. I'm pretty sure the book came out before the Diablo 3 was launched.
2) I also noticed similarities between Adria and Kitty Kwok. If you have read the series, you probably know what happens to Kitty Kwok and probably can make the same assumptions with Adria the witch.
3) I know many players of Diablo 3 want an expansion character that does both melee and range attacks. My thinking toward this is to have a character that can shape-shift into different animals (like the characters of the Four Winds). For exampe, a character could change into a tiger or snake/ turtle and have melee capabilities or change into a dragon or a phoenix and have range attacks.
Anyways, I loved reading these books and I hope everyone gets to read these books as well.