Gazelle’s dance does not prevent stacks. It’s the same thing with Skadi - she will still be able to put stacks on your heroes even if they are under Gazelle’s dance.
Stacks are stacks, they aren’t status effects. Do a long press on a heroe or an ennemi with a status effect and a stack and you will see that they are shown in two different sections.
This way a heroe can also have both a defense down status ailment and a defense down stack at the same time. Can be handy for titan fights