For Thunder I would rather take Baal U than Mammon.
In general:
Fire: Svarog
Wind: Titania or Cybele U
Thunder: Baal U
Light: Sol or SSArty (but I wouldn't mtix light here)
Dark: Pluto
Water: Hard to say, Snow Raphy seems like a good option, from healers I prefer Aphro's skill set, but Poseidon semi-covers debuffs problems, so Nike U may be a better option.