Ah, Granuaile's Sneak Attack is usable as a temp til you get Sniper Shot and Cassiopeia is actually a priority to get too for her Chaos Magic (removes 1 enemy buff) so it saves you the trouble on the way to D'art.

I don't think any of those other himes are very useful though, aside from maybe Perun for mitigating overdrive damage and the other dark SR healer, who I would assume is Ereshkigal, though she's easily replaceable since you have Osiris but can work as in a fill in til you get better/more dark units.