Human is the baseline against which species should be compared. This is especially true of species directly derived from Human, such as Demigod and Mummy. Therefore this post compares HuNe to DgNe at XL1.

XL1 HuNe
EV12 same, but he can't easily get EV13 like DgNe
HP13 MP3 HPr.04 MPR.08
Str8 Int15 Dex13
UC AED vs adder: .3
leather armor increase spell failure from 4% to 6%
ring mail 13%

XL1 DgNe
HP14 MP5 HPr.04 MPr.09
Str11 Int19 Dex16
UC AED vs adder: .45
leather armor 4% to 5%
ring mail 10%

Dg wins on points max, spellpower, armor tolerance and melee damage. Advantages are proportionately significant, too. No wonder he makes a much better Necromancer!

Plus, DgAM is incentivized to train Fighting to primary immediately to leverage his +10% HP and convert it to Pain damage. Which helps him make use of early weapons.

The Necromancer background is really a death knight who fights alongside his fragile skeletons to preserve them, so Dg's meleeist prowess fits.

The upshot is that DgNe can Necro snowball the whole D:1, trusting his skeletal reinforcements to rescue him if he pushes too deep while his HP and MP are low.

The theme of Necromancy is self-sufficiency, which fits atheist Demigod.

Of course, HuNe catches up once he can worship Kiku. However, rN+ foes counter HuNe Kiku, who remains a weaker meleeis than DgNe. Human is better off delaying high-level spells in order to wear heavier armor.