Is this homebrew feat, Overheal, balanced with regard to other feats?

Is this homebrew feat, Overheal, balanced with regard to other feats?

You have learned to use the healing arts for more than simple recovery post-injury. Now, whenever you use magic to restore one or more hit points to a creature, any healing that would exceed the target’s max hp is instead gained as temporary hit points.

The intent is now any excess healing is not wasted but instead turned into temp HP for damage mitigation. For example, say we have a cleric with this feat and a friendly rogue. The rogue is missing 6 HP so the cleric casts Cure Wounds and rolls a lucky 8. This cleric also has a +3 to Wisdom so now normally the rogue would be healed to full and that’s it. But with this feat the rogue now also gains 5 temp HP.

Is this significantly more powerful than other feats and/or is it potentially gamebreaking with higher level spells such as Heal being used on a target at full health to give them 70 temp HP?