I think that the most fitting class for a succubus, conceptually, might be Rogue. Skilled, relies on trickery and surprise, not primarily a warrior but potentially an effective one.

Min-maxing a succubus is more a matter of adding your Charisma bonus to whatever you can. Marshal and Blackguard, off the top of my head, are obvious choices. (Not Cha-based spellcasting, though. Obviously actual caster levels would be better for that, and you've got spell-like abilities usable at will already.)