Fight V'lad on the platform inside the glowing ring. NOTE: 30th October 2012, it was NOT necessary to fight him inside the ring, and fighting him anywhere else vastly reduces the difficulty of soloing this NPC. Be careful of his frontal AoE which does a high amount of damage. A flying gnome will periodically spawn in the next room and fly towards V'lad. When the gnome reaches any player, it will instantly die, causing a small AoE knockback around where it dies. It is better to kill the gnome in the hallway away from the rest of the group, so that no one gets knocked off the platform.
NOTE: Mercenaries don't get affected by the knock-back, so if you can send in a merc or two and stand back using ranged, the fight becomes quite easy (at level 90).
Approximate HP is 2,890,080