Abominations are not the only type of undead construct there is though. That's like saying Paladins already use various types of Holy Light, or Warlocks use an assortment of Fel magic abilities and minions. That's never gotten in the way of Priests or Demon Hunters having their own variations of abilities. Have you even noticed that Demon Hunters 'summon' demons with their Covenant ability, which they sacrifice? That's normally a Warlock thing. Guess exclusivity over a theme isn't as big a deal as we all thought.
Besides, are we really questioning whether Necromancers could have their own variations of constructs? There's plenty more that we've seen like Bone Golems, Fleshbeasts (Rotface/Festergut), Flesh Titans, Fleshhounds, and more. Heck, Putricide himself is a great example of potential Necromancer gameplay, throwing alchemical ooze puddles and animated oozes on the ground and plenty of poison gas. Unholy DK in comparison is all about summoning minions and attacking with them, with plague spreading being a very minor aspect of the spec. Necromancer's Plague spec could be all about poisons and gasses while supplementing zone-based damage with minions that shepherd and gather minions into staying in the puddles.
That's actually pretty cool, since it shows that Necromancers have a much wider range than we ever knew them to have before.Oh, and by the way:
A Forgewarden of the House of the Chosen sharpening a Runeblade
"Some of these necromancers also seem to take on the path of the warrior, fighting with blades or riding atop massive beasts."
However I'd point out that I specifically called out House of Rituals, Constructs and Plague as the themes I'd choose for a Necromancer concept. Not sure why you're associating the House of the Chosen since that's more associated with Warrior characters like Draka and Mograine. I mean, I'm not surprised there are melee variations of Necromancers in the house of the Chosen, since that's where all the warrior types seem to be. Not what I consider an archetype for the Necromancer class concept, I'd say.
Same with House of Eyes, which seems to be themed on spiders, spies and Rogues. I wouldn't associate that house with Necromancers either. Rituals, Plague and Constructs are what we normally associate with traditional Necromancer archetypes, though I must say the melee variants are interesting to point out.