I don't think Vi is too strong, I've played about 150-200 games of Vi in the past 6 weeks or so, I just started playing her and wanted to get good with her. I can say that her kit is just really good for the jungle. Her shield is an extra 250 hp or so on her first clear, she can can Q through raptors and double E to instantly kill all the small ones, and if she Qs through Krugs right then the smaller one will get stuck between the big one and the wall until the bigger one is killed. A healthy and quick early clear leads to a decent game if played right. In my opinion, Vi is in a spot where any jungler should be, completing a full first clear and having 50%+ HP left. She's not OP, other champs just don't have the jungle tricks, AOE clear, and shield. As far as her damage to champions go, my comment is unrelated to whether or not she's balanced there.