Azurill, Marill, Azumarill, Meditite and Medicham should have their Attack stat doubled and their regular abilities (Huge Power, Pure Power) replaced. This allows for more variety in these Pokemon since one ability would not ultimately dominate.
Shedinja's base HP should be increased to a decent level (Base 50?) and HP and IVs should work properly. It would make Shedinja much more viable and not immediately killed by status, entry hazards or weather.