Sona's winrate has gone down to 52% due to Aery nerfs
http://euw.op.gg/champion/sona/statistics/support
Just so you know that's lower then the average winrate she has held for the last year, she held a consistent 53-54% during the Ardent meta and was not seen as a problem
Just food for thought considering she has quite a devastating nerf coming her way in the PBE, perhaps one could hold the opinion that it may be a little overkill for her current position on live