Unless anyone has any great advice on how I can beat Oceania, I'm willing to cede the game rather than micromanage a losing battle against elemental royalty and angels.
If this is becoming too tiresome for you you can turn AI if no one else object. I do understand your situation and would like to salute a brave ennemy. You were in a leading position but you did one fatale mistake: to rely too much on your demons and undead chaff.