Soraka feels awful to play now, as a support...
I love playing Soraka, having accumulated 1.6mil mastery points on her. I own every skin and every chroma for her (excluding Winter Wonder's Ruby chroma b/c I was in a financial rut at the time and couldn't make it). My nickname for the past 16 years is Star, my favorite color is purple, and part of my ign for League includes Star in it. I absolutely love and enjoy playing Soraka, she was my very first buy when I first started playing in spring of 2010, but now...
It just feels so detrimental for the team to pick her, it feels like. I was low on mana before hitting level 2, and I remained oom after hitting 2 due to the enemy team trading with us. Not only that, but I was also extremely low on health, and couldn't afford the risk of trying to land Starcall without dying. Healing has always taken its toll on Soraka, but Rejuvenation helped remedy that a little bit so that you could continue to do your job as a dedicated healer.
Now, not so much anymore, as you lose so much mana trying to sustain yourself and keep your lane partner alive and healthy. Starcall costs a ridiculous amount of mana for what it offers Soraka now, coupled with the 20 reduced mana per level, and even the reduced movement speed Starcall gives now makes it so hard to get away from the enemy when you're trying to rebuild your health back up, or just trying to escape, because now it's scary to attempt to trade with the enemy team.
I get Soraka was out of hand top lane, which wasn't her fault at all but the current state of top lane instead. The changes she received were aimed at kicking her out of top lane while trying to maintain her role as a support. The aim was off, however, as I and so many others called out. Soraka struggles to perform as a healer now, given the tools she needed to survive were cut down hard.
Early game is too hard as Soraka now, and transitioning into mid game is even harder, because you're so dependent on trying to max out Starcall and Astral Infusion, but you can't leave Starcall at rank 1 because of its long cooldown and the minimal health and speed it gives Soraka and her rejuvenated ally. Maxing out Astral Infusion first hurts, maxing out Starcall first hurts, and alternating between the two hurts, and even then you're constantly low health and low mana and it's too risky to try rejuvenating yourself anymore.
I really hope a Rioter sees this and comments, and helps Soraka out, because she feels terrible to play as now. She needs help, and I realize lolalytics isn't accurate, but she went from S tier to B- as a support, from a 53% average win rate to 46.55% win rate. If you were willing to hotfix Yuumi and Akali to get them in line after their heavy adjustments, I don't see why you couldn't for Soraka.
Allow Starcall's Rejuvenate to enhance itself by 25% per champion struck beyond the first. That, or revert her entire nerfs and move Rejuvenate onto Astral Infusion instead, so that Soraka can't function top lane without maxing out Astral Infusion, which in turns hurts herself more by not being able to max out Starcall first instead. Please help Soraka, Riot.
TL;DR - Soraka is in a horrible state right now, post-nerfs. Hitting her top lane while maintaining her support missed the mark by a mile.