Diviner is easier(less hard (I tried it myself once)). You can miss most conjuration spells, but when you can't cast evocation spells, well, you'll have a problem (on some of them). As a diviner, you will still have fodder, btw, you can still charm a lot of your enemies
But still, if I were you, I would take the necromancer
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There's something in your eyes, ah no, I see now, it's the reflection of my deadly gaze - Mirac Honorguard
(Necromancer)