Would there be any opportunity to overhear any valuable gossip about the bandits or the Deemers?

None of the NPCs will have much to say about the Deemers beyond general grumblings of distrust or an occasional more personal story of how a friend or relative up and joined them without warning.

As for the bandits, characters who listen closely may hear the weapons dealer at Corbucci's speaking to his employees using suspicious phrases like a "special delivery" for "special clients."