Never left. Having said that, the characterization of Thor is cringe-worthy. I don't mind the occasional replacement character like Jane as I didn't mind Masterson, they're just temporaries who eventually go away after their stories have been told. What I don't like though it how Thor's and Odin's characters have been twisted. I understand development must happen, but that was just bad. And it's not Aaron's fault either, this started right after JMS left the book.
Aaron has just made what Fraction started worse.