By the way, Fog Warriors also easily counter Banishment.
Of course, Shinuyama is still better. I think the problem is that lesser Oni are just too pricey to be really useful. But then, if they would be more easily massable, it could be overkill... As for Banishing demons it's quite thematic and Oni MR is on par with other Demons.
Considering nations:
EA: Agartha, I think. Maybe Fomoria.
MA: Oceania, until...
LA: Patala. Maybe Arcoscephales - I just don't see Sybils as good substitute for what they had earlier...