Dammit, I had a truly massive post, and the forums ate it. Lemme see if I can reconstruct it well enough:
The book you wanted sourced: http://www.imperial-library.info/content/skyrim-annals-dragonguard
2804: Upon the outbreak of the Winterhold Rebellion, our Master refused orders to send the Dragonguard out to help supress the rebellion. The Emperor ordered our supplies cut off, but we have made arrangements with the local Reachmen and are effectively self-sufficient. The Grandmaster supports our Master's action on the grounds that it violates the Oath of Allegiance.
This is Emperor Kastav. I have no idea if he was Dragonborn, and he seems to come between Reman I and Reman II. Maybe it was a Regency? So I can't say for sure that they directly disobeyed a Dragonborn, because I literally can't find any other information on this guy.
This book does make numerous references to dragon sightings/slayings, so the Dragonguard were doing that even after swearing allegiance to Reman.
http://www.imperial-library.info/content/skyrim-atlas-dragons
Herein is recorded the list of known dragons, both living and dead, including those slain by the Dragonguard since the time of its founding, as well as those slain in earlier ages, where they can be identified. Unfortunately, only a few of the dragons slain by our Akaviri predecessors during the Crusade were recorded and thus this list is sadly incomplete.
Once again, the Dragonguard were dragonslayers. Odahviing is listed in this, which is presumably where Esbern gets the name. Also:
Paarthurnax - The legendary lieutenant of Alduin in the Dragon War. He is now known to lair on the Throat of the World under the protection of the Greybeards of High Hrothgar. Master Araidh continues the established policy of avoiding direct confrontation with the Greybeards while waiting for an opportunity to exact justice upon him.
The Blades have been after Paarthurnax for a VERY very long time. They don't want a confrontation with the Greybeards. You, however, are not only able to get past the Greybeards, you're able to get right to where Paarthurnax roosts. You may well be their first opportunity to ever really go after him.
http://www.imperial-library.info/content/skyrim-book-dragonborn
Lastly, we come to hte question fo the true meaning of being Dragonborn. The connection wit dragons is so obvious that it has almost been forgotten - in these days when dragons are a distant memory, we forget that in the early days being Dragonborn meant having "the dragon blood." Some scholars believe that was mean quite literally, although the exact significance is not known. The Nords tell tales of Dragonborn heroes who were great dragonslayers, able to steal the power of the dragons they killed. Indeed, it is well known that the Akaviri sought out and killed many dragons during their invasion, and there is some evidence that this continued after they became Reman Cyrodiil's Dragonguard (again, the connection to dragons) - the direct predecessors to the Blades of today.
Dragonborn have been known as great dragonslayers in the past. The Akaviri that became the Dragonguard slew many dragons when they came to Tamriel, and there's evidence they kept doing it after joining Reman.
http://www.imperial-library.info/content/skyrim-thalmor-dossier-delphine
Background:
Delphine was a high-priority target during the First War, for both operational and political reasons. She was directly involved in several of the most damaging operations carried out by the Blades within the Dominion. She had been identified and was slated for the initial purge, but by bad luck was recalled to Cyrodiil just before the outbreak of hostilities. During the war, she evaded three attempts on her life, in one case killing an entire assassination team. Since then, we have only indirect evidence of her movements, as she has proven extremely alert to our surveillance. She should be considered very dangerous and no move against her should be made without overwhelming force and the most careful preparation.
Operational Notes:
She is believed to still be working actively against us within Skyrim, although we have no location on her.
Nearly two hundred years after Martin's death, the Blades were actively working against threats to the Empire, IE. the Thalmor. Delphine hasn't been idle, and the Thalmor believe she's still working against them. She's not just wandering around looking for the Chosen One.
http://www.imperial-library.info/content/skyrim-thalmor-dossier-esbern
Esbern was one of the Blades loremasters prior to the First War Against the Empire. He was not a field agent, but is now believed to have been behind some of the most damaging operations carried out by the Blades during the pre-war years, including the Falinesti Incident and the breach of the Blue River Prison. His file had remained dormant for many years, an inexcusable error on the part of my predecessor (who has been recalled to Alinor for punishment and reeducation), in the erroneous belief that he was unlikely to pose a threat due to his advanced age and lack of field experience. A salutary reminder to all operational levels that no Blades agent should be considered low priority for any reason. All are to be found and justice exacted upon them.
Operational Notes:
As we are still in the dark as to the cause and meaning of the return of the dragons, I have made capturing Esbern our top priority, as he is known to be one of the experts in the dragonlore of the Blades. Regrettably, we have yet to match their expertise on the subject of dragons, which was derived from their Akaviri origins and is still far superior to our own (which remains largely theoretical).
Again, the Blades weren't sitting idle and inactive. In addition, the Blades' dragonlore surpasses that of the Altmer, because they were originally Akaviri dragonslayers.
http://www.imperial-library.info/content/skyrim-rise-and-fall-blades
Many classic texts tell us of adventures to Akavir, known as the dragon lands of the east. Many from Tamriel have attempted to conquer it, most famously Emperor Uriel V and his Tenth Legion in 3E288 as documented in the Imperial dispatch "Disaster at Ionith." Dragons have long been legend in Akavir, and many believe that their brief appearance in Tamriel's history are those that escaped Akaviri, for it was there they were hunted and killed off by the Dragonguard. The Dragonguard would follow those that fled to Tamriel in the late 1st Era.
Again, their origins were as dragonslayers.
They protected Reman with their lives, as well as his descendants, as the Reman Dynasty ushered in Tamriel's 2nd era. It was through these years that their reach extended, and their order grew to become the Blades. Their conquest of the dragons complete, they only sought to protect the Dragonborn, and through him, the Empire.
Their purpose became fully focused on the Dragonborn and the protection of the Empire AFTER all the dragons were wiped out. Dragon slaying was still a focus for the Akaviri Dragonguard, even after finding the Dragonborn.
The Empire of the 4th era no longer saw the Blades openly protecting it, or the Emperors. That role is now filled by the Penitus Oculatus, a purely Imperial organization. But the Blades continued their secret work, to watch for the Dragonborn and guard against future enemies. The Blades were among the first to see the signs that the Thalmor of the Aldmeri Dominion would not remain isolated within their borders forever. They could do what the Penitus Oculatus, servant to Imperial policy, could not, and thus earned the lasting hatred of the Thalmor.
To guard against future enemies is important here. This is the reason they were acting against the Thalmor. Note that Delphine's reason for wanting Paarthurnax to die is that he could very well turn traitor again.
As the poster above pointed out, 'guidance' does not necessarily mean 'slavish, unquestioning devotion'.