Level 85 Shaman took him down with Tier 5 Merc and pet. Modestly Geared, 24K Mana 25K HP unbuffed, 1300 AAs. He popped from the trap in the Northwest corner back behind the pyramid. I clear the area of mobs around the traps before I trigger them.
My strategy required some repetative buffing prior to triggering each of the traps along the North wall (thus potentially spawning the Fabled).
1) Lassitude on Merc and Pet 2) Wild Growth on Merc 3) Spirit of Panther (or Lynx) on Merc and Pet. 4) Halcyon Whisper on Pet, Me, then Merc.
Trigger trap. I would run over the trap and keep moving to a safe pulling spot far enough away to hopefully not get immeditate aggro from the Fabled Prismatic Basilisk.
1) Cast Healing Counterbias or Balance of Discord on Fabled 2) Epic click 3) Heal the Merc, Refresh Halcyon Whisper, HEAL the Merc! DoT Fabled, HEAL the Merc! Refresh Panther or Lynx, HEAL the Merc! Recast Balance of Discord on Fabled half way through the fight. DoT Fabled. Keep Healing the Merc!
The fight took about 2 min. Had an add start beating on me at the start. I slowed it and ignored it; just kept Healing the Merc first and foremost. Ended the fight with 31% Mana left. I would say this fight is less difficult than soloing named yard mobs in Field of Scale.