The Succubus has no elemental resistances or weaknesses, so your highest-damage elemental spell will work - a Skeletal Wall and Limbs of Lead will help keep her and her nasty kiss attack from landing.
I nuked her with Rank 5 Elemental Hail (although I only got that from using spellbooks). It took about 5 seconds to kill her.
http://www.youtube.com/watch?v=-f6nqk4KwK8
