Will powers like Cultist's Allure and Wide Sweep be used by any future combatable characters that may be added, or should I go ahead and use Arona and Quin and steal them from their copies?
Per The Observer, most stealable Powers will eventually be implemented in repeatable encounters so if you don't grab them from the Lureling fight you should still be able to get them at some point in the future, we just have no idea when that might be.