I'd say they have Death themes for certain.
That's where i disagree. Voodoo would not be part of the Necromancer, but part of the Witch Doctor/Shadow Hunter.No one said the Necromancer is not associated with Void. Necrolytes are Necromancers that use the power of the Void. It's literally stated in the WoWpedia page.
A Necromancer in the lore is someone who seeks to perfect the secrets of undeath, and there's no limit to what form of magic (or science) to do so. This is why Alchemy, Void, Blood Magic and even dark spiritualism (Voodoo) would be sufficient themes for a Necromancer. It's like how Paladins channel the Light differently, different races could tap into Necromancy in different ways.
It's all still maldraxxi death-themed, not different cultures.Shadowlands has even expanded on the various subthemes of Death-based magic.
There's no particular reason to include necromancy either, since there are other magic types unaccounted for.I pointed at the existence of Melee variants of the WC1 spellcasters existing as playable classes in WoW. I even explained how the pattern was not fool-proof, so I'm not sure why you jumped to the conclusion that we 'need' melee representation. I was merely making a point that we have multiple classes that use Fel, Holy and Elemental magic. There's no reason to exclude Necromancy from that.
The Death Knight is merely a plate-wearing, Runeblade-wielding Warrior? heck, then there was no reason to add it at all. -_-And I didn't make any case to exclude Nature at all. I pointed out that it doesn't exist in the RTS and the closest comparison would be the Druids of the Claw, since there is no formal 'Green Knight' archetype in the game, nor does the game necessitate it being created to fill the niche. All the while, a Spellcaster who uses Necromancy is well defined since WC1, and carries the theme with far more breadth than just applying it all to the Death Knight, which is solely a Runeblade-using plated warrior.