Sona Mid is pretty good this patch.
Now, before you read the rest of my opinions remember that I'm not saying to go try this in ranked because it's 100% viable, I'm just saying that you can play it more than you could last patch.
I think Sona mid is pretty good right now because of several indirect buffs:
1.)There are a lot less tanks that Sona has trouble with. 2.)Buffs to Sona's base mana regen make one or two Doran rings all you need for mana regen items. 3.)Sheen now costs less gold, while Lich Bane still offers good AP and also gives CDR now. 4.)Windspeakers works in perfect sync with Sona's W, as you get the increase in both healing and shielding. 5.)There are less waveclear mages than there used to be, slightly hiding Sona's weakness of having lackluster wave clear.
And before someone says "well yea it works in low elo because silvers and bronze don't play well",my team went against high elo players (not like challenger but definitely not low elo)
https://i.gyazo.com/da205528306a67469ed167a79350806b.png
I chose Windspeakers because we had Soraka on our team, so I thought I should try to maximize sustain to keep the adc alive (worked out pretty well).
I like to call Sona Mid a 'utility assassin'; she can burst pretty well, while offering tons of utility with AP-heavy heals, shields, and movement speed buffs.
Try for yourself, preferably with a Soraka support.