I think it is pretty simple. Put her Starcall heal to scale on ranking up Q instead of W. That way Soraka players will have to make decisions about whether or not they want to heal themselves or their allies and not get free passive sustain by just maxing ranks in W to get the best of both worlds.
Pretty simply really, the dev(s) who reworked her set out some pretty clear design principles for her. As long as those are followed, she should be balanced and healthy. If they're not followed (doesn't seem like they are right now), then she might be balanced but also unhealthy, which would probably result in her getting more nerfs until she's trash tier. If the latter happens, she might get reworked again, except this time she'd be reworked by the same people who failed to balance her properly in the first place (I'm assuming there are different designers now since the devs don't seem to be following previously set design philosophies).
That idea has been thrown around before. But it doesn't really fix anything. A lv 1 Q heal would still provide enough sustain when combined with her items/pots/masteries/etc. for her laning phase to continue unchanged and she can continue to max W first. After the laning phase she simply has to max Q second and she will be right back where she was.
She can't be balanced with her current kit, it's just too strong. She heals for far too much far too quickly. She'll be perma-banned until they rework her.
