Curses have been expanded a lot recently, and I feel like it'd fit the 'morally ambiguous swamp witch' vibes of shaman to give them access to Bestow Curse and Bestow Greater Curse. I also feel like shaman is a fitting class for green hags, and playing a hag who can't curse people just seems kind of sad.
The spells themselves aren't that strong, and on a spontaneous caster there's a notable opportunity cost to grabbing them anyway - let people live out their evil swamp hag dreams please...