Fherin the Ancient (Advanced Solo)

Fherin the Ancient is sustained by two Planeshifters; one at each side of him. You have to completely drain the mana of the planeshifters in order to out-dps the healing they do to themselves and Fherin. As a Warlock I used Absorb Magic to drain their mana, it took about two casts per mob. Don't forget to drain Fherin's mana as well. Once out of mana focus on killing the planeshifters and once they are dead kill Fherin.