Frankly, Sona's rework has been a disaster. There are two reasons for this. First, it has totally failed to address her biggest issue (she can't use her power because she's been made so squishy that even creeps are tougher than her, so closing is insanely risky). Second though, it totally abandons her identity and attempts to homogenize her.
I'd like to discuss the latter issue, as it's the bigger concern for me (numbers tweaks can happen after the rework anyways, but a total failure of kit is much more severe). This is from today's post going over the rework:
>Instead of hanging back and winning a war of attrition during laning...
To me, this sums up the entire reason this rework has gone so badly. The team in charge completely abandoned Sona's identity. Sona [i]is/[i] the attrition support. She was initially released into a metagame that was heavy on poke, and her ability to provide incremental advantage to her team made her the strongest support in the meta in short order. This quickly established her identity, which remained mostly constant throughout all her nerfs (because lets be frank, about the only buff she has ever received was the secondary effects to power chord). The ability to provide sustained damage and health defined her, and it made her stronger the longer a fight went on. It also provided her inherent weakness, as she was significantly weaker than other supports in short fights because she needed multiple cycles of casts for her output to overcome theirs.
If we look at supports as a whole, this is relatively unique. Soraka is undisputedly the queen of burst healing. Taric focuses more on boosting armor than heals. Janna and Lulu provide powerful CC and shields to protect teammates. Compared to other healers though Sona is able to provide significantly more health in the long run at the cost of burst heals or clutch shields, and this was the main factor differentiating her from the field.
However, with increased cooldowns, and an apparent focus on the clutch and burst, her identity is being completely abandoned in favor of homogenization. Of making just another Soraka. This is not a musician, a constant source of power. This is just another generic healer. It is, frankly, running away from difficulty. Rather than keep her identity and work to balance her, I feel that instead the team has chosen to take the easy way out, make her the same as everyone else, and shove it live. This of course, while completely ignoring the issues she's had as a result of previous balance changes, and in fact adding mechanics that require playing in ways those issues don't allow.