So you want to know how to handle Soraka top?
I play and main Soraka top/mid since season 6 (well rather mid/top with some ocassional bottom since last season) . Check me on op.gg if you don't believe me.
I was ALWAYS called a troll and being reported everytime we lost. "It is your fault because you don't provide damage", "becase we have no frontline", "because we have no adc (if I played bottom)", "because you trollpicked" etc. I play in EUNE so you guys never met me but those who did and won agaist me never considered my pick to be overpowered. Yes some were suprised that Soraka is so strong early. But that ends around level 6 or 9 or 11 depending on the matchup. And in many matchups if you fail and die early, you are done already and the game is most likely lost too.
So, now that we all know what is Soraka good at thanks to pro play (but saying that she outscales you is nonsense, she has no scalings she outscales nobody lol). So what is she bad at?
She is bad in 1v1 against bruisers, fighters and Juggernauts if she has no flash and does not hug tower. She is bad against AD champions and AD assassins especially (although I have a good results against Zed in mid). She is bad at pushing towers, splitpushing and defending the splitpush. She struggles against flanks and suprise engages, she struggles against burst and wombo combo teamcomps. And she sucks if your carries lost their lane. You won't magically win with Soraka top/mid when your bottom went 0/6 after you ulted them 3 times in 2v2 and toplane went 1/4 as well. Other toplaners probably won't have much chances in such situation either, but definitely higher than Soraka.
How can you abuse Soraka top especially.
First of all, if you play a tank like Maokai, Malphite, Orrn or Sion you can't do much you are probably never going to kill her if she is decent, most Juggernauts are in same position. However it is a free cs lane, she is never going to kill you unless you are really bad. If you have this champion you might want to swap a lane if possible. There is no reason why you couldn't go with Garen into mid if enemy team picked Zed or Irelia or the new abomination Sett. Obviously you need to persuade the typical midlaner who can't play anything else to go top but that is different issue and that should definitely not be an issue in pro play (yet it is and she gets good matchups where swap would fucked her).
If you don't play champion she is good against then, either go all in very soon if you have the champion for it like Trynda or Riven or Jax. Make sure to go all in after she uses Q to last hit minions and that you don't get hit by it. Soraka has only 2 abilities in sololane (not counting ult) and she just used one so there is no way you lose the trade. Force her to use summoner spells and then freeze or all in her with summoner spells again and net a kill. The second option of course requires some ranged vs melee matchup knowledge (that toplaners generally lacks) and experience with fighting Soraka and avoiding her E. You might need to do this twice as her E has really long cooldown so first engage you are luring the E and the second engage you can kill her.
If you have a jungler who can carry and she does not play totally defensive sacrificing cs/xp and staying under tower, call him for free kill everytime you force a flash out of her. If she do hug tower and sacrifice cs keep the lane frozen and deny as much XP you can from her. Prefferably you want to kill her with the lvl lead you gain, but it is not needed just denying cs is great tool to make her useless. Her items might be cheap but if she is 3 levels behind main carries then it won't accomplish much and she will be easier to kill in teamfights.
Alternatively, push and get a river control, do herald - if she comes you should win the 2v2, because she is maxing Q first her 2v2 is not that strong until lategame. Use Herold on toplane she can't kill it and if she tries all in her and punish her for it.
Generally speaking you don't want to tower dive Soraka but some champions can do it easily. Tryndamere and Kled are good examples. Junglers like Elise or Lee Sin are also very good against her.
Later in game when she gets ultimate your primary job is to force her to use it against you and to track her cooldown. Soraka has very long cooldown on her ultimate, even with 20% cdr it is over or close 2 minutes (depends if she has one or two ranks). Therefore constant teamfights are bad for Soraka, and if she doesn't have ultimate when there is a Dragon fight her team should not win that fight. So the best course of actions is to time all in against her with the timer for objective you want to take. Dragon in 1 minute? Lets all in Soraka, force her to ult defensively or die, and then either push the lane and tp or recall and walk to the objective on foot. She won't even be able to take the tower if she stays top, if she joins she has only heals where she puts no points untill she maxes Q so she is basically useless early.
Alternatively, if your bottom is losing hard and your mid has no prio either, you want to create a slow push and dive her with a help from your jungler and take first tower. At this point because you have 2 losing lanes the chances are already bad for you but because it is Soraka top the only action you can do is much easier than it would be normally. Especially if she doesn't take barrier but TP (I always play with barrier, tp is useless in soloQ and it is much easier to dive/all in and kill her as well).
In teamfight. You want to either burst and oneshot Soraka herself - which requires flank or her being positioned badly. Or burst her carries. Ever since lethality Soraka sucks against AD assassins they are oneshotting too fast and out of nowhere. Obviously you need champions or builds to do this (which is not happening in pro play for example - and then they lose to Soraka top). If you have the burst possibility, depending on your damage either kill soneone and make it 4v5 where the enemy team has 2 supports (which should be almost always a fight you win) or if your damage is not high for oneshot yet force her to use ult to save the ally/herself. If she does that, you already gained big advantage. Overally burst is really good against Soraka ever since they nerfed W so hard it is now on 8 second cooldown. Most fights in last season were decided in less than that meaning I could only heal once + ult and that was it.
If you don't have the burst possibility or you decided you go tank Lee Sin etc. because it is normally safer option nowadays. Then what you want to do is to force fights in jungle (where are multiple walls she cannot jump/dash over. Flanks are also great against her. Alternatively you need to split the fight so she cannot heal everyone but need to choose or just run chaotically trying to heal at least someone.
In the end, Soraka played as second support in sololane is making the fight looks very polarized. You either lose really hard, or you win in a fashion where peoples are like wow that was awesome. I often get a 4 honors in a game we won, if we lost I received lot of vulgars and report (threats). So I suppose that is why peoples are now saying Soraka is broken when they saw G2 playing it and how it ended.
Pro play speifically, I think the main problem is that they don't want to change the meta. They keep playing champions Soraka is good against like Aatrox or Orrn and are not swapping with mid when that was an opportunity (LB would destroy Soraka, Aatrox might maybe get a better matchup against Sett but well we all know already how overpowered is he...). They don't play assassins at all with maybe exception of LB, and they are not really fighting in lanes unless they know for certain where the jungler is and he is elsewhere. And when they teamfight they teamfight 5v5 or not at all.