@Riot, Meddler, What is the context on the Soraka changes?

When she was reworked a little bit ago, into the kit where her W had a small mana cost, but cost health, I recall her designer described her like a motor. Her Q converts Mana to Health by landing it, and her W moves her health to her allies. She kind of slept with this for a while, before eventually becoming soloqueue cancer.

But now her kit doesn't function that way, and her W has both a mana cost AND a health cost. I understand that she was too strong, and that she deserved nerfs, but I don't think that this was the right way to do it. There was a simple elegance to the way her old kit works, and now the fact that her W has a relevant health cost AND mana cost makes it so that it never feels good to cast. I feel as though if increasing her costs was the direction that you felt was what you wanted to do, then her Q mana cost or her W health cost should have been increased. Not the mana cost on her W. Her W mana cost should always remain low, in order to keep the feeling of "Q converts mana to health, and W moves health from Soraka to allies" gameplay.

What was the reasoning on raising the mana cost on her W, rather than another cost elsewhere in her kit, or any other changes that may have been on the table?