If it were just that Chronicle had said Necromancy is most closely associated with Death magic, or something similar, I would agree; however, Chronicle is fairly specific:
The above excerpt is basically saying that Nature magic is Life magic, and that Necromantic magic (Necromancy) is Death magic; Nature magic pulls from the Life domain as a source, Necromancy pulls from the Death domain as a source. This is reinforced by the cosmological chart:Originally Posted by Chronicle, vol. 1, The Cosmic Forces
Now, the cosmological chart isn't perfect. For instance, we can see that the Shadowlands is given a similar relation to Azeroth that the Emerald Dream has, and the Titans themselves created the Emerald Dream. Nowadays, we know that the Shadowlands is the universes realm of Death and is (likely) the source of Death magic. We also see that this chart has an elemental type which is not encountered in game, such as Decay, and the chart is not inclusive to all elemental types we know of, excluding more esoteric beings like Murmur, a Sound elemental. That said, the chart is fairly clear in its relation of types of magic and beings associated with them. If we broke a few down:
- The Light is the source of Holy magic and is the native plane of the Naaru.
- Disorder is the source of Fel magic and is the native plane of Demons (The Burning Legion).
- Shadow is the source of Shadow (Void) magic and is the native plane of the Old Gods.
- Death is the source of Necromantic magic (Necromancy) and is the native plane of the Undead.
We run into this problem where Necromancy and Undeath are now decoupled from Death. It's a weird situation because, if we acknowledge the Chronicle cosmological chart as still being canon, it implies that Fel magic and Demons might not have a close association with Disorder or Titans and the Arcane might not have a close association with Order. This isn't to say that beings of a given type are always tightly coupled, as state transitions between these forces do exist, allowing beings from one force being able to transition to another. An example of this could be Sargeras and the Dreadlords taking in Fel magic and becoming demonic entities or Naaru becoming Dark Naaru or Void Gods if sufficiently drained of Light magic (although exceedingly rare). Similarly, state transitions can also occur to mortals. Mortals can be raised as undead, mutated into void creatures, undergo apotheosis to become demons, or infuse themselves with the Light.
The TL;DR would be that one of two things must be true about Chronicle, given the new lore we have:
1) Some of the Cosmological chart is not accurate (which is already true in some cases) because the new information we have about Necromancy breaks the pattern which exists for every cosmic force.
2) All of the Cosmological chart is not accurate and there is no tight coupling of sources of magic, types of magic, and extraplanar races.