Well something else you'd have to take into considerations is if he did in fact try to heal himself of the problem, he/she'd be bound to have massive problems, for instance
If you are in a really dark room and suddenly go into the light, your eyes tend to hurt, now if you have been blind and now can suddenly see you are bound to have some problems
As for the character, I had an aunt who needed a hearing aid for a good portion of her life, she would typically keep it kind of low, but years later while getting a new one, the volume got turned up, and she could hear so much more, this in turn drove her to have some difficulty sleeping because she could hear so well now, so if the character got his deafness healed he would technically have some problems.
As for characters with flaws, maybe I am just a crappy RPer but in my opinion a chartacter with flaws such as these would just slow the game down tremendously, not something I would highly advise. It makes a gap in the party with them most likely not being able to communicate for lack of sign language, even if the character could speak how are they supposed to talk back. It just makes for too many slow down points IMO.