Ive been playing Vi on the PBE for the last day or so, and I have to say that I really enjoy her. She will be an awesome top lane, and an amazing jungler (her clear time is pretty great). My one problem with her is that for the amount of damage she does, she is not tanky enough. For a character that has to get down and dirty into the fight, she gets melted so quickly that it's very difficult to last long enough to do any real good.
While I understand that you can build tanky, by doing this, there is no real way to do damage. It feels like you can only either build her as a squishy melee in fighter that gets melted, and does almost no good, or a tanky tank who tanks tanks all day, but does no real damage.
I understand that maybe I'm mistaken, and just haven't been playing her, right, but this is just my experience. Feel free to leave your suggestions for Vi here and let me know what you think.