I had a hard time dealing with that Robert Plant duet stuff. I much more enjoy her singing with Yoyo Ma.
Robert Plant is about a half step above the Rolling Stones. Frightening, really.
Not questioning your tastes (I’m a true believer in the subjective nature of this topic), but did you give Raising Sand a couple of solid listenings?
I was a tad put off the first time I listened to it (after I bought it of course), and it took a couple of times through before I really got it.
Another singer it has taken me a few listens to get is Neko Case. Highly recommend Middle Cyclone.