Going by champion.gg. I don't really trust lolking/op.gg's statistics.
http://champion.gg/champion/Quinn/
Middle Quinn (you know, where Riot designed her scalings and power curve around) ended at a 46% winrate last patch. You're right, top Quinn's numbers did actually somehow even out since I last looked at it (It was sitting at 46% as well in the middle of last patch), not sure how.
Otherwise, you might be right. I think the smoke screen mechanic is a bit strong when combined with her Q, and really it seems even lower counterplay than the blind she had before. We'll wait for more data and find out by the end of the patch.
But I do think buffing her was the right call, even if they overdid it.