As far as Derek "always" getting good partners...
I don't know about that.
I wouldn't say that Jennie Grath, Shannon Elizabeth or Joanna Krupa were naturals. Or even Brooke.
I think the guy just happens to be an amazing dancer and choreographer. Just like Julianne was.
Nicole, for me, was the only true ringer. But, then Mya was, as well, and she didn't get paired with Derek.
And, somehow, I just can't equate learning a dance for a movie almost 30 years ago to being a "ringer" on this show.