Well I think there has been a healthy amount of debate on this subject.
There isn't much new evidence or new theories I have yet seen that cast more light on this.
I would contend that not everyone, perhaps not even most, consider Drakul to be an Outsider. At least when I suggested the idea I got a fair amount of disagreement at the notion. I would say the going theory is that he is a Dragon trapped in human form.
However as I have outlined before, I myself don't think that is the case. I do think Jim is deliberately being misleading when it comes to Drakul in book, and people are reading into somethings more than they should.
I suppose in response to your theory and kbrizzle's etc. I would ask: Why do you think that a dragon would have a son that would create a Vampire Court (or join one) in order to impress it? Why would a dragon (at least in the Ferrovax sense) even care about such small things?
Ferrovax type of Dragons were semi-divine guardians of the universe. I think they have more to do with Angels and that level of things than the mortal end.
And I challenge that the WOJ you cited is fairly conclusive evidence of them being Dragon related. It is only really conclusive that Drakul isn't really human at all - despite the original canon being that he was a scion, Jim later contradicts this.
Entirely unhuman could mean anything that isn't a carbon-based life form, or anything that shares very little DNA with us. Entirely unhuman likely means a being that is well beyond the human life-form, like an Angel or God or Demon. But we have no idea.
As I have said before, I think Jim's language in that sentence gives a bit of a hint to his origins myself.
Also just to correct you, the Outsiders have never specifically been called Dark Gods. They are almost always described as alien, something completely different from anything inside reality. They are more than mere demons, their thinking is so bizarre that it is beyond comprehension. In theory. The Old Ones, who are the rulers of the Outsiders (and may be Outsiders themselves - but this is a little unclear), were trapped. A race of demon gods who once ruled reality. Indeed it seems that while their foot soldiers (the Outsiders) were banished beyond the Outer Gates, the Old Ones were trapped here. Trapped.
Who else, indeed what else, was entirely unhuman that got trapped here? Sounds like a big nasty Outsider or Old One to me.
Besides I haven't seen anything that connects Dragons in general to Outsiders, directly or otherwise. Whereas the Black Court (and all Vampires shown so far) seem to have strong links to the Outsiders, particularly the Black Court.
I would also again like to point out that Michael's exclamation "Blood of the Dragon" was more like a curse or swearing, rather than a specific statement of origin. Indeed he never uses it again. And the old french word Dragon comes from the greek word Drakon and latin Draco, meaning sea serpent and large serpent respectively. Which is why the Devil in the Bible is often called both the Dragon and the Serpent, as the original translation was the same word. And often Christians both in the past and present call any sort of non-christian, unholy being a spawn of the Devil. And the Devil has been conflated with the Serpent in the Garden of Eden and with the Great Red Dragon of Revelation.
So my money is on him being an Outsider, or the Devil himself bound in human form.