By your definition I wouldn't call Deism a religion; because I don't know of any (organized) rituals partaining a Deistic Deity (as opposed to, I suppose, a theïstic deity). Which is actually fine with me. Most deists I meet seem to somehow stand closer to atheists than theists. I think that's due to the ritual thing you mentioned. In order for something to be a true 'organized' religion, one must not only think that the supernatural is real but also that what one does in the natural world can affect this supernatural domain. Rituals and such as prayer, mass, weddings, ... are all supposed to gather the benevolence and approval and love of this deity and seemingly can affect his mood and mind. And even when you don't think prayer, confession, mass, ... is necessary per se, there's often still the idea that how one lives life (as in a 'good' way opposed to a 'bad' way) will define the afterlife, or at least will affect the feelings/order of the supernatural entity.
That being said, the greater flaw in that definition, to me, seems that it takes 'supernatural based practices' and turns them into religion. Ghosthunting, accupuncture, reading aura's, ... all have a system of beliefs and rituals relating to the supernatural. Yet I would not call them religions, though all are bullshit.