Coercer: use dispel when he reflect's on mainmob (be careful with damage); you can not interrupt him, when he's casting; charm one of the adds; target him directly for the whole fight and damage the adds with AOES to make him damageable. If you target the adds directly the main name doesn't take any damage.
Illusionist: Mezz adds, dispel doppelgaenger, cure and interrupt. The fight is simple. Keep the adds mezzed and burn down the doppelganger. Avoid or turn off anything that will break mez, like AEs, AOEs, and maybe autoattack. Use the single target mez on all the adds. Then burn down the doppelganger. When mez wears off on the adds, rinse and repeat.
Warlock: Talk to your doppelganger, Rift the add's, ascension your doppelganger.
Wizard: start with dispel on mainmob (otherwise dmg immune), as soon as the adds (6 sets?) appear, ae damage to kill them, then kill mainmob with an ascension
Necromancer: There will be three large sludges once the encounter begins. Send your pet on one of the sludges, and use AOE to kill your doppleganger. Do not target the doppleganger directly. If you see a message that says your pet is attacking the wrong sludge, switch to a different sludge a repeat the steps above.
Conjurer: Dispel on main mob, send your pet in on whichever sludge Planar Armor has been shifted to. AoE on main mob. Dispel on main mob, will often move which sludge has Armor. Leaving your pet on the same (even correct) one too long is an auto-death.
Retrieve the planar empowered weapon from the statue in Arcanna'se Spire - Zone out of Planar Fragment and click altar again