so with cards like Black Forest Bats, for example.. Can Dunhere still attack them while in the staging area? As his ability is already bypassing the normal combat rules?

No, Dunhere's special rule allows him to bypass the part of combat that requires the player to be engaged with an enemy. That is the only part that is affected. This is a separate requirement and must still be fulfilled.

If an attack is left undefeated though, the damage still goes on a hero, correct?

Zjb12 said:

Yes, that's correct (if "undefeated" should be "undefended")

Ha ha! Yes! Stupid iPad spell correct! Should have been undefended.