I think in terms of damage, Soul Masters will be the best since they do have that Elemental Resist Debuff skill "Undine's Garden" but they lack the one thing that makes Light Skills overpowered, and that's "Shield of Heaven"
For Dark Lords, I think it's hard to find good High-Level Dark Attribute equipments.
Out of the 4, I would go for Water/Lightning/Light Witch.
I got an EVIL AP Speech Balloon Head
Number of the Beast