I really don't think there's a single, definite answer on the matter. Each roleplayer has their own preferences on the style of RP that they enjoy, up to and including the average "power level" of the characters they interact with. To a person playing a more gritty angle - perhaps a struggling Thaumaturge pouring over tomes just to learn how to throw basic fire and ice spells, or even just someone who believes that someone can't learn two or more "conflicting" styles of magic (or any types of magic not openly stated in lore) - Sasha could be considered "overpowered." Conversely, those that play up the high fantasy side of the game and have more fantastical characters - those who have faced down Primals or have a laundry list of skill sets, for example - might see her as more on par or even underpowered.
Not to mention, how it is handled and displayed will also either aid or hinder the OP/UP view of the character. Emphasis on the strengths versus the weaknesses in RP, the descriptions of how the characters act in conflict, and even just general opinion of the masses based on hearsay of the character/player could add to that. Focusing on her stores of arcane knowledge and her unique powers could give the "feeling" of being OP, heavy emphasis on her genetic condition can give the opposite.
In my own, personal opinion based on the levels I've dealt with? I feel she's about par - she has traits that make her unique and provide her with skills to utilize both in and out of combat to a solid degree, but she also has defining "drawbacks" not only in her genetic condition but also how she interacts with others in certain situations. The entire package sort of... balances out, to me. Then again, I try to give any type of character a shot, so I'd be harder pressed to define an OP character that wasn't openly just a list of negative attributes.
... And I have characters like Judge and Gogon in my stable, as it were, so I feel I can't be too nitpicky about OP traits. Glass houses and stones and whatnot. And even then, they also set up a good example of "it depends on the other character." Even "depowered" as Gogon was after his stint as an event Final Boss, he's pretty powerful compared to some and not so much compared to others.
tl;dr: It's all relative, really.
Not to mention, how it is handled and displayed will also either aid or hinder the OP/UP view of the character. Emphasis on the strengths versus the weaknesses in RP, the descriptions of how the characters act in conflict, and even just general opinion of the masses based on hearsay of the character/player could add to that. Focusing on her stores of arcane knowledge and her unique powers could give the "feeling" of being OP, heavy emphasis on her genetic condition can give the opposite.
In my own, personal opinion based on the levels I've dealt with? I feel she's about par - she has traits that make her unique and provide her with skills to utilize both in and out of combat to a solid degree, but she also has defining "drawbacks" not only in her genetic condition but also how she interacts with others in certain situations. The entire package sort of... balances out, to me. Then again, I try to give any type of character a shot, so I'd be harder pressed to define an OP character that wasn't openly just a list of negative attributes.
... And I have characters like Judge and Gogon in my stable, as it were, so I feel I can't be too nitpicky about OP traits. Glass houses and stones and whatnot. And even then, they also set up a good example of "it depends on the other character." Even "depowered" as Gogon was after his stint as an event Final Boss, he's pretty powerful compared to some and not so much compared to others.
tl;dr: It's all relative, really.
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