I don't know if it's just me, but any healer shouldn't have to rely on crit heals to perform well. Most games I've played, heals couldn't crit, kinda felt weird coming into this game where it was possible. However that being said, when a heal do crit, I think it's just a nice bonus, like a Freecure proc or a Enhanced Benefit II proc.

When it happens, it happens, when it doesn't, oh well, not like I needed it =3.