She did get challenger tho, so with that i got massively outplayed by a girl who's 10 years younger than me. FML, i'm old and bad.
In regards to Sona support, i feel like she's become a niche pick. She works against the likes of morgana, janna and lulu, but still gets completely crushed by tanks like Thresh, Blitzcrank and Alistar. Once you go low in lane, people will try their hardest to dive you because you're a squishy support (much like how you deal with Soraka) so playing lane is even more important now, because we all know a Sona playing from behind is useless as fuck.
I don't think we'll ever see Sona in competitive play again consistently, she is just so inferior in a premade 5v5 setting compared to other squishy supports and she is easily punished by people with 200 IQ. I fear she will be reworked completely at some point, simply because her kit is too simple. Compare her to someone like tresh, kench or morgana and you easily see why nobody would ever consider picking her in a tourney.
That said, I've been having a ton of fun playing her again, she is my favorite champion by far and even though she is lack-luster in terms of kit, she still has that massive poke/sustain potential along with hard engage. Also considering the current adc's being played (kai'sa, ezreal, tristana) she can work in solo queue at least in the bonobo heaven i'm currently in.
If anyone is encouraged by this and wants to play her i have a small guide of what i've been doing so far.
Rune setup: http://www.lolking.net/runes#?selection=sorcery|8214|8226|8234|8237|inspiration|8304|8347
Note that i dislike Absolute Focus, because MSPD is still king on Sona in Season 8 (as it much was back when mspd quints was a thing). Also i'm not sure if the 5% cdr/item/summoner talent is the best, but i get a hard-on by having 45% cdr in late-game for some reason.
So what do you build? Well, it's pretty much game-dependent now, there's no generic build and you shouldn't be building the same items every game, so i'm just gonna list the items i consider the best for her and when i get them.
Redemption - When they have hard engage and burst and you know 5v5's will be rough, get this item. A well timed redemption will save lives and it can be used while you're dead, so even if you get dived and die, you can still pull it off.
Ardent Censer - Just get this, whenever your ADC is fed and/or your team is auto-attack heavy. It's so fucking broken when you are ahead, i rarely rush it when i lose lane simply because you want more durability in the case of inting.
Shurelyas(?) Reverie - So happy that this item is back in the game. AP and health are two very useful stats as AP enhances your heals/mspd and health increases your durability (you knew that, didn't you?). The best part is obviously the active that allows you to engage/disengage. Get this when it´s hard for your team to get close in fights or when you're scared of getting run over by the enemy.
Locket of the Iron Solari - Beast item. Gives you resistances that compliments well when paired with redemption/reverie and the active is probably one of the best in the game. I recommend getting this AFTER you have gained some health unless you're super scared of getting bursted down by the likes of Syndra, Zed etc.
Chalice of Harmony - I don't really buy this anymore unless i need crucible for team fights. It used to be one of the core items for Sona, but giving that spellthief's upgrade paired with the Manaflow Band rune, means you don't really have the same kind of mana issues that you had in previous seasons.
Boots - With the new runes you get boots for free thanks to Magical Footwear and usually i just rush mobis right after to be a roaming beast. If you dislike mobis get CDR boots, though you should learn sooner or later that MSPD is king on Sona.
Gold item - Spellthief's all the way. Coin will never ever be worth it. Every time you hit Q, you get gold, so the more aggressive you are, the more gold you net.
My skill-order varies depending on my match-up. Against a disadvantageous match-up i personally prefer QWWE, R > W > Q > E because you won't win a poke fight and you'd rather have the heal in case you get engaged on.
However if i have the advantage i go QWQW, R > Q > W > E taking a point in E at level 8. This is similar to what you did in previous seasons and i feel like it works smoothly. I rarely regret not taking a point in E at level 4, because if you wanna all-in somebody you just flash R anyway and the slow-power chord becomes negligible (at least in lane). You want to maximize your poke/sustain and that's what you wanna play around in lane.
I don't think tank-sona ever will be meta again like it was once. Sure you could make it work in a game or two, but even if i'm behind i don't consider "tanking up" to be a way to deal with annoying enemies as you'll prolly just die anyway. Feel free to prove me wrong though *cough* teutonica *cough*
As for Sona mid, it's very gimmicky but she does have some good match-ups. I've never really been much of a mid-laner so if someone has tried this, share your wisdom. Be aware that you need massive fucking skills to last-hit and most people will shove you under your tower, knowing that you'll probably miss most of the creeps. She did get an base-AD buff, but if this is to become a trend, she needs more help.
The build i've been using can be found here: http://www.lolking.net/runes#?selection=sorcery|8214|8226|8234|8236|resolve|8473|8430
I really prefer gathering storm, as it just racks up your burst potential when you hit that 2-3 item core. Getting there is hard though, so scorch could probably be used as a replacement if you need to be a threat early on.
My item build has been something along the line of Archangel -> Lich Bane -> Deathcap, then getting zhonyas and void. When you hit that lichbane powerspike you start doing absurd damage with your Q and power chord and most people don't know how to deal with your massive damage output and high sustain. They will often be surprised too.
Sona is definitely in a very interesting spot right now, but until they give her hard-CC she will never be seen in tourneys. She remains a solo Q stomper, reliant on having a good early game (similar to someone like shaco). If you do decide to pick her up, i really advice to be careful when you pick her. Blind-picking her as 1st/2nd pick is super fucking risky and that risk just keeps going up the higher rating you are. She does have the potential to outright shit on certain supports like Janna and Lulu aswell as shitting on ADC's that can't poke her back.
I do hope RIOT looks at her from this Sona mid perspective and perhaps give her some quality buffs to make it more viable. It would definitely be interesting to see her in mid in pro play, but for now it seems unlikely.