When you have elemental advantage, using one (1) Character Attack Eidolon isn't all that bad.
I'm personally running Ygg and a pure Defender weapon against Ult Water, taking my bonus HP to a total of +66%. It's usually enough to keep me alive until snakes (thanks to the free potion). Annoyingly, I can only survive snakes if somehow I don't have Water res- at that point which basically never happens.