Weapon Doesnt Matter, armor doesnt matter. (I would however suggest using some of both
Skill Slot 1 - Mend Ailment (Cheap to cast on yourself for zealots effect, and divine boon effect, and Doppleganger wont use it at all)
Skill Slot 2 - Elite Skill - Echo (Nice, but not absolutely necessary. Speeds kill along.)
Skill Slot 3 - Zealots Fire (Damage dealer)
Skill Slot 4 - Life Attunement (Just to reduce his attacks.)
Skill Slot 5 - Divine Boon (So you can heal but he cant, since only monk spell is mend ailment and he wont use it.)
Skill Slot 6 - Retribution (Self Explanatory, deals damage back to himself.)
Skill Slot 7 - Balthazar's Spirit (So you can gain Energy from his attacks)
Skill Slot 8 - Blessed Signet (To replenish your energy so you can cast 1, 2, and 3)
Set Smiting Prayers at Max (Mine was 13 (+1 head)).
Set Divine Favor at Max of what is left (Mine was 10).
Before you step on the last stone cast 4, 5, 6, and 7, then use 8 until your energy is full. Skip visual, then immediately attack, cast Zealot's Fire as soon as you are next to him. Then use echo and immediately cast mend ailment. Then you can alternate between the two till he is dead, using blessed signet if you need more energy. He may run, follow him or Zealots will not work.
The only reason I used Echo, not arcane echo is because I didnt know if I would want to double cast blessed signet, so it is up to you.