Smokescreen and shadewalker are amazing in high-end savage raids. It is pretty much required in order to let a DRK play dps-optimally while maintanking, as it reduces the amount of required powerslashes/Grit uptime needed to maintain hate. Removing both would be a pretty big hit in ninja's raid utility, so unless you want to make ninja worse for a sudden, shadewalker and smokescreen should stay.