It's not that his voice being artificially deepened is the problem, it's that there was no need for it to be changed. How does no longer being confused make someone's voice turn deep?
My point was when it's obvious a voice has been altered in some way, it sounds really bad. Corypheus isn't too bad compared to some other people, but it's still obvious and his original, unaltered voice sounded better. Maybe they thought keeping the voice at its normal pitch would have given him away, but since we first saw him in a memory, they could have stuck with a deep voice for that, but gone back to his original voice when we officially meet him in person.
Changing the pitch of a voice causes a lot of sounds and tones to sound odd or off-key when they would have sounded normal in the original voices/pitches. I'm just saying it's very jarring when it's noticeable, and it should not be used as liberally as Bioware used it in this game. Excluding demons and such, it really doesn't have a place in a Dragon Age game.
Sorry for the off-topic, all.