Hi there, Soraka has been my favourite champion and main since I started playing league and I have stood by her despite her rework and all the nerfs she's gotten. I just really disagree with these current changes on the PBE. Soraka isn't overly strong in the support role atm and these changes hurt her in the support role much more than in the top lane. Not to mention they once again force her into a max Astral Infusion style of play which forces a passive playstyle in lane which isn't fun or interactive.
My personal wish is really for Soraka to be reverted back to an earlier rework Starcall format. Where her Starcall projectile was slower when cast at a distance and faster in melee range and she only got the self heal if she landed her Starcall center on her target. Remove the movement speed buff but keep the slow only on center hits and make it so that when she hits multiple champions in the center she gets multiple regens instead of the old burst heal. This moves her back to a more skill focused iteration where she succeeds or fails based on her ability to properly land her Starcall but it rewards her for landing it properly on multiple targets. This change would also help with her top lane dominance since dodging the center of the Starcall allows others to win trades against her and avoid the slow while the removal of the movement speed means she can't just back off easily once engaged on. Keeping the self heal as a regen instead of a burst heal would also mean she won't just instantly win trades solo laning or in botlane when she lands a Starcall so there is opportunity to burst her down.
I really disagree with the mindset that champions who find success in other lanes suddenly need to be gutted. Stop gutting champions and instead add more skill expression into their kits. Nobody wants to play a champion that has no skill expression and you are just pushing Soraka back into this state where she's going to end up building Warmogs again and just sitting there spamming her Astral Infusion whether or not she actually hits her Starcall and that isn't fun or healthy for the game.
Alternately if you are dead set on these solo lane changes to gut her ability to exist outside of the support role, I propose an alteration that doesn't gut her current support style and doesn't remove her ability to have multiple skill leveling options. Keep the nerf to her Starcall self heal and nerf the movement speed buff to 15% at all ranks. Make it so that when she shares the rejuvenation effect with her Astral Infusion the regen and movement speed double on herself and her ally. This maintains the current amount of healing she has while maxing her Starcall while still preventing her ability to sustain in a solo lane.
It still nerfs her self sustain in the botlane since she has to choose between healing her ally to get the full regen and losing that precious mana early.
The 30% movespeed at all ranks when sharing rejuvenation will help her kite a bit better in early 2v2 skirmishes to make up for the regen loss but makes her more vulnerable without an ally. Remove the proposed mana changes for both Starcall and Astral Infusion and the removal of the max health self damage when under rejuvenation since that makes her too oppressive in a max Astral Infusion build.
I feel like either sets of these changes would maintain Soraka's current relatively balanced support state while still forcing the player to either show more skill expression or make decisions on mana management in lane vs sustain while still reducing the oppressive aspects of her solo lane fighting style. I would also like to iterate that nerfing Soraka's healing ratios whether on her Starcall or her Astral Infusion almost always pushes her back towards a Warmogs playstyle every time she has been changed this way. Maintain her AP scaling on abilities or reduce the base and increase the scaling because it promotes her to build a squishier build that is much easier for the enemy to burst down but also gives her a strong presence in the game if the enemy fails to take advantage of that fact. Keeping her self damage on casting Astral Infusion is important to promote her vulnerability since late game even if she lands a Starcall with a high AP build she can't cast Astral Infusion indefinitely if the enemy ignores her but if you remove it then she loses that vulnerability.
I apologize for the long post but I hope that someone on the balance team can at least make it through and take it into consideration.