Yeah, I noticed this last summer. I think the tree will be good for a while after it is dead, but of course you wouldn't want to find out the hard way that it is no good.
As for rapping down to the Death Ledge, there are scores of natural options. In keeping with the spirit of the place, just go out and find one if you don't already know a few. In addition to many excellent trees, one can set up bomber gear anchors and remove them on the way out.