If you need a healer, keep Aphrodite in your party.

For your Soul, probably Mordred with Sniper Shot. Since you have a lot of debuffs, having access to debuff- is really good. At least until Hercules' Relic weapon, that is.

If you're going to swap anyone out, it'd be Saraswati. But since you don't really have anyone to swap instead of her, I don't really see the point. Belphegor for some content maybe, but at least nothing so far would need Belphegor to cut those Rage phases.