Subsumed ability will depend on the comp; It's between Smite, Shock and Eclipse.

[Banshee] is hard to build. She's one of the frames I'm most unsure of as her builds tend to be rather situational, to the point of even adjusting range to fit tilesets.

Must have mods: PFlow, PCont, [Stretch], [Resonance], SubsumeAug([Smite Infusion] for Smite)
Exilus will be [Power Drift] or [Cunning Drift], depending on build.
Aura will be [Power Donation] or [Energy Siphon], depending on setup.
That still leaves 3 undecided mods.
Good mods for those 3 slots: [Umbral Intensify], [Blind Rage], [Transient Fortitude], [Overextended], [Augur Reach], [Streamline]