Healing Magic Skill just adds to cure power. Each tier of Cure has its own soft cap on how much healing magic skill adds, after that it's only incredibly small amounts. Cure 1 ~ 4 reach their soft cap rapidly, Cure 5 has a much higher cap but it still exists. That's the whole reason BLU's M.Fruit and P.Embrace scale so well with healing magic skill, they have the same caps as Cure V but start at a much lower cure power. What SE needs to do is lift the caps and even out the scaling. It'll take more skill to go up in cure power but the soft cap would be much higher.