I would rank demon lords such as Orcus and Demogorgon as divine powers, on the same playing field as gods like Tempus et al. but perhaps a little weaker. Otherwise I don't see how the Upper Planes wouldn't have conquered the Lower Planes by now (apart from the infinite abyss thing).
If the Great Wheel is intended to maintain a symmetry of power, then major demons and devils (and other alignment exemplars) have to be more powerful than just epic monsters.
IMC, the "exemplary" exemplars(like the virtues) are deities. I mean, a deity is basically a critter powered by "belief energy", right? What are exemplars made up of? Belief. And, considering that Powers have maybe a few hundred thousand followers per world(and only a few Powers expand beyond one or two), while the only thing required before Elysium gets boosted is someone who thinks killing people are bad, m'kay? Now, most of this belief goes into the plane itself, but its' extensions(read, LotN, Primus) get a rather nice piece of the cake, too.
*e*
Oh yeah, something abit off topic, but whatever: where do you get those FF avvies?