I'm wracking my brain on this one because it sounds super specific and cool, but honestly? I don't think it's a common blend at all. Necromancers are usually brooding in towers or leading armies, and dancers are grace and life. Having a protagonist who's both feels like it should be a bigger thing! The closest I've stumbled across is in LitRPG/Progression fantasy where classes can get weirdly mixed. I recall a web serial where the main character had a 'Dancer' subclass that augmented their magic, but it wasn't specifically necromancy. Maybe in some anime or manhwa? There's often characters with death-themed powers who are also agile fighters, which feels adjacent. For a proper book, I'm coming up empty, which is a shame because the visual of a character using intricate dance movements to command the dead is incredibly compelling. Someone really needs to write this.
Actually, wait. It's not a perfect fit, but T. Kingfisher's 'The Saint of Steel' series has paladins who serve a god of death and some of them are described as moving with a deadly, graceful precision. Not dancers, per se, but that lethal grace vibe is there. The protagonist of 'Paladin's Grace' is a perfumer, which is another art form, so the author definitely mixes violent vocations with artistic ones. A necromancer dancer would fit right into that world. Maybe we just have to wait for someone to publish it.