Sadie, I agree with Greg and Pat.  The dryer the better to a point.  The more dense Osage I've worked has seemed more brittle (not the right adjective).  As I worked it with a draw knife the wood seemed to pop off in chunks, as opposed to the slices on less dense wood.  I believe it was/is the differing densities and character of the wood more so than MC.  Having run into the same issue you are having I can only say I work more slowly with the draw knife, scraping more and digging less.