I think the problem here is that too many people are familiar with the animated version of Raven, and not her original comic book characterisation. Up until now the animated Raven was the only Raven audiences outside the comics had really seen. There's a level of disconnect that's very jarring.
Personally, I don't have a problem with Injustice's version of Raven. It's spot-on character-wise as she has fallen to her base demonic impulses. The disconcerting voice is a clever move in my opinion; when I first heard it, I knew immediately that something wasn't quite right, and really set a creepy tone for the fight against Catwoman.