You don't really need to disincentivize them, but add real, functional counters. Firesweep and Dazzling Staff are absolutely terrible to play against, especially on 3 tile movement units. But on their own, they're manageable, it's just everything around them that makes it hard.

To that end, add anti-dancer structures that work like the Schools. Hell, add anti-assist Schools, and let the player have one movement type school and one assist school. You could disable healing assists, movement assists, refreshers, or rallys, alongside the unit type debuff. It'd share the same column mechanics that the unit type Schools do, and actually maybe make people think about their def team instead of slapping horse+dancer on.