Necromatic Conduit and Sceptre Allies in Presence Effect not being an Aura

An Aura is a an affect affecting certain chosen kinds of unit in range from it's source.

In case of Necromantic Conduit the source is the player, in case of Sceptres the source is the Sceptre wielded by the player.

Like every single of this effect is literally an aura by definition.

Yes none of them apparently get affected by Aura Magnitude which means for some reason the game does not recognize those effects as auras.

This look clearly like a bug. I've performed some tests over this by picking the Magnitude from the tree and none of the values which should be affected by potential aura change got affected.

Both of these effects explicitly apply to allies "in your Presence," which is its own stat that is scaled by Presence Area of Effect. They are not tagged or defined as auras.

Sometimes, skills that take effect in your Presence are classified as Auras (like Purity of Fire), but not all such effects are unless the skill says that it creates an Aura.

If a skill does not create an Aura, it won't be affected by aura modifiers.