Her not having a unique voice isn't going to hold her back. Most artists sound like someone else and it didn't hold them back. Tink's biggest obstacle is Timbaland. Timbaland is a legendary producer, but he's hurting Tink more than he's helping her. It's one thing to giver her a co-sign, but he's already making grandiose statements and comparisons that will turn people off from her before they even hear one record. It's not Timbaland himself, it's the fact that he needs to let the music speak for itself. Let the fans decide to like her based on what we hear, not him telling us what we should think.
When I look back on Timbaland's track record with breaking artists, the ones that are successful are ones that he didn't go out of his way to hype up. I don't recall him making much fuss over Ginuwine or Missy. People liked the music because it was dope on it's own merit, not because Timbaland told us it was hot. The marriage between the artist and the production is what sells artists to fans, not because we're told to like it.