Hmmm are you reading it properly?

Restores own HP and the HP of all nearby party members. Potency varies with current Confession stack.
1 Confession: 150
2 Confessions: 300
3 Confessions: 450
There is a 20% chance that party members (including self) are granted a Confession each time you heal their HP via Medica, Medica II, or Cure III.
Confession Duration: 10s
Can only be cast when at least one party member (including self) has a Confession granted by you.

https://na.finalfantasyxiv.com/jobguide/whitemage/

Try it on fates with choco 20% is very low but I have seen it.