Yes White Mage should get Banish IV, Banish V and Banishga III. Their damage, MP and recast needs to be reworked to be in line with the other elemental nukes, approximately the strength of Aero. Paladin can just be treated the same as Dark Knight and elemental magic.

On a side note, I would also support the creation of a line of dark nukes that use dark skill and are accessed by Black Mage and Dark Knight.