As an 85 Solo-Mage + Merc I took this guy down by myself, but it was not an easy fight. Granted, I did a lot of things wrong. I didn't know that if his back was to me I would not suffer the Rampage damage. Knowing that would have helped a lot. A WHOLE lot because I had to de-focus DPS and mana-efficient damage (casting Rampaging Servants on Gift of Mana procs etc.) and often had to step in and heal with the Merc.
But I did indeed take him down and finally got the Gloves of Dark Summoning that I have been waiting 8 years for. Take THAT TVK.
Sony, please change the respawn of all bosses to 1 day at the most.
Watch out for lots of traps in his hall that pop mobs out of nowhere.