Best Charms for Asuras:
Dawnfire Asura: Freeze (Ice), Wound (Physical), Zap (Energy) or Divine Wrath (Holy).
Midnight Asura: Poison (Earth), Zap (Energy).
Hellspawn: Freeze (Ice), Curse (Death).
Frost Flower Asura: Wound (Physical), Poison (Earth), Enflame (Fire).
About the question "what to do with the frost flower asura" as a paladin, you should use "exana amp res" if there is any space in the box, and if you want to maximize the exp, ignore the ones that run away, try to go from box to box, just finish the ones that are far away while you're luring or going to the next box, they don't afect the overall hunt that much.