Isaiah and Goeddy - completely agree. Wrong click and you go walking towards the enemy like you're going to give them a hug, instead of attacking them. "Shit! Why?" Haha. edit: I have accidentally healed an enemy also.
So far I'm loving having my melee dude with "Zombie" and super high fire resist. I have him charge in for multiple knock-downs, then have my two casters cast poisons and fire all over him. Heals him a ton and blows the shit outa everything around him :)