Don't forget Power Split! With 0 Attack and Spec Attack EVs and IVs and Will-O-Wisp, Cofagrigus shuts down Physical sweepers Completely. Night Shade always deals damage according to your level, but has one immunity. Dusknoir also has better coverage, but if you're going to choose a Physical Wall, go with Cofagrigus. Dusknoir for Mixed Walling. They both work very well, but Dusknoir has more offensive moves with good coverage as well.