There are a few other ways. If you have bards you can cut down on the dps your kiters take by highsunning the blood drinkers, but your kiters a ways from where you tank redfang, bards with the kiters, and bards highsun the blood drinkers as they get close to knights, knights kite for a bit if the blood drinkers get them. Things you need to be careful of here, is keep a druid or ranger and your healers for the kiters all bunched up with the bards/knights, a few voricious will spawn with them, just root and be done with em.
Otherwise, just put more healing with the knights, and burn redfang hard if ya don't have bards!