Technicality, but I think as Edda was a WHM, and the PotD was Gelmorran, that Necromancer should technically be a corruption of white magic, rather than an alternate version of SMN.
The SB WHM quest line touched on raising the dead as a corruption of conjury. It even uses a staff/cane like weapon.

So I'd say WHM is to Necromancer as NIN is to Thief and WAR is to Berserker.