Blackfuse is the catalyst behind an entire expansion. Gazlowe is the engineer behind the Horde capital, and has been a major force within the Horde for years and now leads the Goblins within the Horde. Mekkatorque is the leader of two Alliance races and had story points in BFA.
But yeah, they're as inconsequential as Darkmoon Faire characters.
Which is purely opinion based on zero facts.
They'd use intellect to construct advanced machines for protection, damage, support, and utility. Common sense.
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Necromancer class already exists. It is the Death Knight class.