I'd probably try to tune it in a way that on turns where the breath attack is used, it lowers the chance for the tail swipe or something like that. Or maybe I'll add one turn to the cooldown of the breath attack.
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It is too powerful for a one turn cooldown. maybe if it didn't cause ignite, but as it is, it needs a 3 turn cooldown to make it remotely viable. Also, get rid of the free turn it provides, that is functionally making it like the boss gets two turns in one move. No matter how difficult you want a boss to be, they should follow similar rules to the player to give it a fair chance.