Two rules: no clothes with artificial intelligence on your head, and at about 50% of the monster's health, use special Celestian magic.
After extensive testing I found:
No clothing on
No Hat (NPC)
Minmax abilities to have +5,10,15,20 Speed and Arcane. (CD reduction helps as well). Since you get no bonus from outfit.
Cast 1 wind magic OR dark magic, then pop Celestial powers and use ultimate magic to prevent mob from running away.
Finish off with light spell.
Rinse and repeat for next article of clothing.