You know, I never really thought about it until I saw it done well in 'The Priory of the Orange Tree'. It's not just about spectacle, though it's definitely that—flames spinning against a night sky before a siege is a hell of an image. But in a functional sense, they're a hybrid. They're psychological warfare, first and foremost. Seeing someone fearless and graceful in the heart of chaos, weaving fire, messes with an enemy's head. It's unnerving.
On a practical level, I imagine they'd be skirmishers or support. They could use their skills to control the battlefield—creating fire barriers, lighting trenches or signal fires under pressure, or even using the distraction to enable flanking maneuvers. Their gear would have to be specialized, too; treated fabrics, heat-resistant bindings. Less a front-line berserker, more a battlefield artist whose medium is terror and ash.
I always liked the idea that the dance itself is a form of combat magic, a ritual woven into movement that empowers allies or weakens foes, something subtle that a straight-up mage blasting fireballs wouldn't think of. It turns a battle into a performance, and that's a terrifying power to face.