No one thought Mouni would fit the role of Sati when articles about her first came out, yet they love her now, so I think people shouldn't judge until they actually see her.
We actually don't know how actors or actresses will look in mytho roles until they have the make-up and costumes on and start acting, but character-wise, Devi Parvathi is not like Sati. She is more like the character of Mata Lakshmi, and yes she was more the docile wife than Sati was, but then again, for what reason would she have the flare up? Raja Himavan was a good father who respected Lord Shiva, so Parvathi could be proud of him unlike Sati, whose father humiliated her.
Some who has a motherly countenance should be chosen for the character of Devi Parvathi.