If a dragon was there, you don't think it would've been interested in a vampire nation claiming the place at its seat of power? You don't think it would've noticed all the folks making a racket on its lawn?

I imagine the general rule about Dragons in this 'verse is "Don't bother them if you don't want to get slapped down." They defend their territory.

That doesn't reconcile with the Red Court just up and claiming a site that a Dragon is on.

I think that:

1) Dragons really don't care much what people / vampires do.
2) I think it may be significant that the one and only time we've seen a Dragon was at a Red Court function where they gave him a very costly gift. 

Or, as you say, it may not mean anything at all!  It just struck a chord with me this morning while listening to the Audiobook. 

What also jumped out at me this time was the Merlin's sudden change of tactics.  For years his MO against the Reds was "defense defense defense", then all of a sudden he's talking about wiping them off the face of the earth.  Hmmm, what happens in the book?  The Red's get wiped out.  Makes you wonder if Vadderung and he had a chat behind the scenes in this book.   

I was listening to Changes this morning and got to the part where Harry does his Gravity Hammer spell at the temple.  Listening to Harry's description of what the power of the Lay-Line he was using felt like, it sounded suspiciously like how Mr. Butcher described what a Dragon in his full form would be like.  So, I wondered if the source of the Lay-Line under the temple could be one of the remaining Dragons???