I think you are right...it is fun to start with "first of all".
But I am not sure we have to look for someone who is powerful....it could be that for the title of "The Necromancer" we are looking for someone who either on his/her own or with help from another necromancer, tries to raise either one being that is super powerful, or many beings all at one. Maybe "The Necromancer" has the grand idea, but needs assistance due to the power it will take to complete the task. I would guess that raising the dead (and thus trying to control the dead) will take a great deal of power. It could be "The Necromancer" is the brains of the operation so to speak.
Or another thought...maybe "The Necromancer" is Josh or another less powerful immortal and it refers to a new title he obtains after receiving training from someone else....we know that there are others out there that are Necromancers, or can talk to the dead. Maybe he gets some training from Perry? Or Dee? and it either goes very right or very wrong, depending on your point of view.