If Dark Charm is played on a hero does it disallow the hero's hero ability. For example Leoric reduces monster damage on anyone within three spaces. If he is dark charmed and attacks 'as a monster' does his hero ability reduce the damage ?

I would think his hero ability should only work when he is in his role as a hero, not when he's been dark charmed into doing the overlord's foul work. It would be like the "good Leoric" is trying to psychically step in to mitigate the damage being wreaked by the "bad Leoric". That seems contradictory. In my opinion, you would ignore the hero ability in this instance.

Hmmm.. Id say all of his abilities that passively affects the outcome of the attack will count. But I would probably use it as a move action 9/10 times.