When you match three hearts, you get your team's combined RCV value in health.
The auto-heal leader skills provide their multiplier to the leader with the ability only, once per turn where any 3 orbs are matched. So:
0.5x: Dryad, Mandrake
1x: Cupid, Angel, Mermaid, Siren, Amaterasu
3x: Siren the Enchanter, Archangel, Alraune
5x: Amaterasu Okami