Mainly to beat most heroic bosses I find that positioning your crew is important. Like with the Snake Boss in GunDrak I leave my crew at the bottom of the stairs and fight him at the top of the stairs by his stone. That way his nova never hits my crew. I drop DnDs on my crew and that aggros the adds he summons onto my DK.

Pretty much every fight except the straight tank and spanks are all about positioning.

Watch a few videos in the movie section and you will see how people position for fights.