True that sheds can deteriorate to the point that they are worthless. If It is showing any cracks on the outside then I definitely would not use It, even if the material underneath looks Ok after turning to size, because the cracking can appear in the ferrule later down the road.
I had a piece of antler like that, and since It was hard, low in pith, and very white, I turned It to ferrules with some other antler just for the heck of It. I thought the cracking had turned out with the router, and kept an eye on the ferrule blanks to make sure, but several days later I could see dark lines where the cracking was starting to turn up.
Sheds are great, and dry is great, but too dry and weathered is not always good either.