Oh yes, these are strong indeed. Roughly the same pain as a Balron Paragon, I would say. Surely not made to solo them - although it's actually doable. They cast Necro spells (of which i.e. Blood Oath and Wither are extremly bad
) and Mage spells too which includes their ability to heal themselves and, as you said, the ability to dispel . 'Least they're bardable and have a Undead Slayer vulnerability which gives a chance to drub them. Try to get rid of the lesser spawn first.
Despite of it all, I think my greed will drive me to the graveyard again and again untill I found these very nice loot pieces
.