One houserule I've used for this: for every die of magical healing, you may also spend one Hit Die (if you have any left.)
In practice, this means a top-level cure wounds, when combined with HD, can bring a character most of the way up to full (ie a 9th-level barbarian getting 5d8+wis+5d12+(5xCon)) - making such a spell actually worth casting. This cause actual healers to be a thing without making them overly powerful.
But ultimately we dropped it, because frankly whack-a-mole, while it does happen from time to time, doesn't get ridiculous enough to be worth the extra brain-load of the houserule.
That, and the more effective in-combat healing becomes, the more it pushes characters who can heal towards looking at all their cool options, sighing wistfully and casting yet another healing spell.