These are dark blue to me as level 47 Paladin, and the toughest and rarest of all the Katta graveyard mobs. I still get about 2% experience from one of these.
Spook and chase is the easiest way to wear them down, using Ghoulbane and Instrument of Nife. If you have a Ranger with you they can snare to make this a whole lot easier, though they are certainly doable solo. Once you get into the groove with the graveyard undead you will understand their paths and how to turn them towards you after they are spooked, so you need not chase them to the other end of Katta. It just takes practice.
This is a fabulous place for Paladins in their forties.