She's ranged vs most melees.
She is 100% relevant throughout the game, regardless of how her laning phase goes, simply because her heals and silences will never ever fall off.
She can bully out melee's because of said range, allowing her to actually be a very dominant lane bully vs most top laners.
And even if she gets beaten into the ground, it absolutely doesn't matter because once the laning phase is over, you might as well set those deaths back to zero.
She doesn't need TP because of her ultimate and redemption, allowing her to stay toplane and not miss farm, and once she gets max CDR, she'll easily be able to just chill up top lane.
Is this Soraka's fault? Is Soraka broken? Is she this unstoppable force that needs to be gutted? Even if you hit her numbers a bit. Even if you reduce her power in lane, it's still very possible that she could still remain topside. Because top lane is a terrible lane that (and I'm speaking in the most generalizing way possible) is the least relevant lane of everything.
If you're going 5/1 on a Garen and you're crushing it top... but the enemy adc/mid/jungle are going 6/0, it's absolutely not going to matter.
Instead of trying to put a bandaid on things by nerfing Soraka (and probably making her useless afterwards) the changes needs to be on top lane as a whole.