As I said, it needs a little brother, that does something similar, without the added benefit.
This way you have a stopgap feat for everyone, and a feat with an added effect for those that have better base stats.
this way, the feat investment for balanced characters is reduced... one way to encourage balanced stats. (This could be a model for melee training too: have strength 15 and you may use your full bonus to damage)
Maybe the feat could be even better:
Special: If your wisdom or charisma is 15+, you may save against...
Also i want to emphazize how important that you may sae, even if it normally allows no save. I hope this wording will find its way into the healing skill and every other extra save mechanic...