Necropolis versus Academy.

The proposed Necropolis build against the Academy takes into account the most likely Academy build options: we don't know how the Academy will develop. Moreover, given the conditions where attacking the opponent before the start of the 4th month of the game is not allowed (and I assume there are no opportunities for scouting), there can be different combinations of magic schools for the Academy.

The education branch leading to the Death Lord enhances the necromancy skill (I don't think I need to explain why this is needed).
Of course, Stone Skin looks better (I agree with this, especially combined with resistance).
Elemental Equilibrium will prevent the Academy from actively using Phoenixes and elementals.

If I understand correctly from your words: why is there no attack skill? Because defense is more important for the Necropolis in a game against the Academy.