Soraka feels the same if not stronger than she is on live when she heals a target that is around 44% health or so due to her percent missing health passive.
However, one of the things I'm starting to notice is how large of an impact healing reduction affects the new Soraka.
Against kill lanes or aggressive lane opponents in general, it is imperative that Soraka and her's allies health is near topped off and here lies the issue.
1) With the new Soraka, when the enemy initiates on your AD Carry there isn't much you can do. You can heal them but the heal is barely worth anything when your ally is above 60% health or so. You can wait until they get somewhat below 50% health to make the most of your heal but this falls into the enemy's plans. One of the first things players do when a target is low enough that they think they can kill is ignite. This is ESPECIALLY true against Soraka. Granted, Soraka has always been weak against ignite but when you combine this with the nerfs to her base heal for the new passive, it makes ignite even more potent against Soraka.
2) Soraka is a defensive support but in order to lower the CD of her heal, you have to go on the offensive which makes you push the lane and vulnerable to ganks. When my lane gets ganked as Soraka, there is really nothing I can do to help my lane partner if they get ignited or if my heal is on CD. All I can do is run beside them. I can silence the enemy but the animation requires that you stop running to do so. Starcall also requires that you stop to cast the animation. When I stop to silence the enemy, my AD carry usually can get away safely, but because I stopped, I'm now in a compromising position and must use a Summoner Spell if I want to make it out alive. I dunno, the whole Starcall interaction with Astral Blessing just seems counter-intuitive to me.
3) Morellonomicon. Now that supports have gold, I am seeing this item a lot more often on the PBE and I'm sure the trend will continue when the support changes go live. The item is a very good purchase and applies an effect that is very detrimental to Soraka, Grievous Wounds. Soraka's passive was changed to encourage strategic use of heals at low health and be less of a sustain bot, but how can her heals be impactful if the enemy support is applying Grevious Wounds to all allies who are below 40% health? Now that Morellonomicon is no longer a niche item, this is going to hurt Soraka's viability.
I don't expect any of the following changes to be implemented, but here are a few suggestions to think about:
1) Nerf the duration of Ignite's healing reduction to promote more skillful use. This change is probably too much to ask for.
2) If a target is selected, make Starcall a single target ability. If no target is selected, it uses the current AoE functionality. This change would allow Soraka to remain a defensive support during the laning phase making the most use of the new interaction with Astral Blessing. During the later portions of the game, Soraka can continue to shred the MR of enemies in team fights like she currently does.
3) Allow Starcall to be used while moving.
4) Allow Infuse to be used while moving. I can typically use Infuse to save an ally, but 9/10 that puts me in danger since I had to stop for a second to cast it.
5) Apply a scaling slow to Infuse. Same reason as the above proposed change. I don't know if you have the tech to do this, but I think it would be cool if the strength or duration of the slow scaled based on how far they were from Soraka when the ability was cast. I think this would help carve out Soraka's niche as a defensive support as the slow would be at it's strongest when it is cast near Soraka but almost negligible if the enemy is at max distance. Or maybe vice versa.
6) Nerf Grievous Wounds on Morellonomicon in some way.
7) Change the armor buff of Astral Blessing back to 3 seconds.
Those are my thoughts.