What does high end raiding have to do with it? An experienced WHM is going to rely on ogcds and regens to do the bulk of their healing in any content. That's how you optimize it, and high end raiding is not required to play your job optimally. When SotL was first released, only Cure 2 gave a 100% proc rate. Cure 1 was still RNG. Again though, your suggestion only returns the lily mechanic to RNG. I know where you're getting at, and want to take away having to use up a gcd to get a lily. But why not just have a regen cast proc a lily initially, while the ticks themselves are RNG for additional lilies?
Correct me if I am wrong, but doesn't Divine Benison require at least one lily to use? That's what my tooltip says. Otherwise it indeed just remains a passive ability you pay no mind to.