Hmmm.. I have to say CRAP to that! I started a new game for kicks today, (trying out a mod called "Alternate Start"), and I, having gotten to High Hrothgar and done 'Jurgen's Horn', have seen 2 dragons spawn...and I HAD TO CHASE THEM ALL OVER THE PLACE, JUST TO KILL THEM!!! No longer do they target you after a fast travel, (they spawn, sometimes), but they fly away if you attack/wound them!!! I am waiting to see if the 'Dragon Rend" shout is as useless as it was by the time I got to the Vamp castle, in my last game.. when I shouted at them using rend, they would just fly away, recuperate, then maybe, and I MEAN maybe, they would come back! This was DIRECTLY RELATED TO THE DAWNGUARD DLC!!
If DLC didn't alter all of the game, why are there Vampire attacks on the towns every night?? Right from the get-go? Also, the guards are incredibly persistent about joining the Dawnguard, so much so in fact, that I have murdered 10 guards already??
Anyway, I am tired and ranting, I'm nearly 60 and I should be in bed..lol Squashy
I noticed after I finished the Dawnguard DLC on the Volkihar side the Dawnguard attacks stopped, the Vampire attacks stopped personally when I joined the Volkihar but this is supposedly a bug on the PC, they supposedly still attack after you complete it on PC.
After that I noticed the dragon spawns returned to where they were in the vanilla game.
I fast travel a lot on my Khajit snow white Vampire named Mr. Whiskers and almost always end up spawning into an area with a legendary dragon flying overhead.