I'm not sure if this has been asked before but can you use hero Dori's defense adding ability with hero Beorn since it targets the defense of a hero and not the hero?
Dori's text:
Response: After another hero is declared as a defender, exhaust Dori to add his defense to the defending hero's defense for this attack.
Beorn's text:
Sentinel. Cannot have attachments.
Immune to player card effects.
Beorn does not exhaust to defend