Even with rhaposdies KIs, the the drops from VW still remain the same. I still count how many times it takes me to kill Morta just to get one riftcinder/riftdross...and not just myself, but with a few other folks. To kill Morta between 10 to 20 (my record was actually 27 kills before seeing one) times for one riftcinder/riftdross is very stressful.