About Guardian Heroes

When using Nicole's healing spell, pink sparks either shoot out from the sky, a circle forms underneath her, or nothing happens at all. Is this a stat-based effect, or due to a certain maneuver technicality?

Prererably, I'd like to have the pink circle healing move to happen all the time. Is there any way to achieve this all the time, or consistently at least?
The only way to increase yoru chances of getting the healing circle is to pump up your luck stat. It's still somewhat random even if you max out your luck. Also if you increase your Intellience you'll get a bigger healing circle for whatever it's worth.