I'd say just go all out with Arthur (Shingen EX). You have quite the overdrive control with Dark Ammy + Satan and with buffed burst, you probably won't have a too hard time killing that rage bar. In this case, Gaia is obviously totally unnecessary & I guess Susanoo would take her place.
That said, that's only working with solo run (or BT).. I guess you can go with that setup for the normal purposes. As for EX, I'd say combo buff from Shingen. I don't really find anything better as you already have enough debuff/defense/heal.. but your dmg might be a bit lacking, and you're slow on burst as well. That might help you a bit with both.
As for me, I will likely just shrug the rage phase off with this setup.
