I dont think you understand the impact of her mutation, she made a deal. In the end it was that or dying. To sustain her she was transformed, basically the crux of her story. She will always have to face what she became in the end. Thats Azshara now.
That one instance, which again functioned as an Illusion literally to fool farondis. A bunch of teleport sounds and some vage assumptions of reversible transformations isnt going to change how it is. I just explained to that this mutation wasnt some random transformation for Azshara, it was life or death. And again sure she is a powerfull spellcaster, but outside this (in the past) Azuna instance we have no reason to believe she is able to undo her mutation or change at will. If that was the case we would have other instanced showcasing that magic, we simply dont.