[Rataxes]

Necromancers cannot use Illusion spells and Conjurers cannot use Divination spells. Normally I'd say a Necromancer is far better since a mage basically cannot survive without True Sight. But since both Jan and Viconia will be able to cast it, I think a Conjurer would be better. There are loads of very powerful and useful Illusion spells (Mass Invisibility, Project Image, Blur, Mirror Image, Simulacrum) . And even though you do have Jan, an expert illusionist, I think you'll have better use of two people who can cast Illusion spells, than three people who can cast True Sight.