Originally Posted by
PsychoBlonde
According to the wiki, hags have Cold Iron DR. On Legendary they also likely have PRR so you'll do reduced damage no matter what you hit them with unless you have something to make them Vulnerable.
Candace heals the other two so you just have to kill her first. She's not particularly tough so if you target her the fight goes pretty fast.
If you free all four of the gatekeeper apprentices, they help you fight and this makes it a lot easier.
Try slotting a fear immunity yellow augment instead of relying on Greater Heroism, that might do it.