The Dragonknight is a class of warriors in ESO. Their Class description reads as:

These skillful masters-at-arms use the ancient Akaviri martial arts tradition of battle-spirit, and wield fearsome magic that pounds, shatters and phsyically alters the world around them.

Now lets get started on these first point.

1. The DragonKnight uses Akaviri martial arts.


Why I think the DragonKnight does not use Akaviri Martial Arts

What exactly is "Akaviri Martial Arts"? I can tell you its not what you see in ESO with the DragonKnight. Its not even close according to what i have red from in game books and lore.

First lets look at "who exactly" invaded Tamriel in the 1st Era 2703(This invasion happened years before The Interregnum)

These folks were the Tsaesci. There are many books that make it clear the Tsaesci are not human, and are not men, but they can "appear that way". If you read Mysterious Akavir, it tells us that:

The serpent-folk ate all the Men of Akavir a long time ago, but still kind of look like them. They are tall, beautiful (if frightening), covered in golden scales, and immortal. They enslave the goblins of the surrounding isles, who provide labor and fresh blood. The holdings of Tsaesci are widespread. When natives of Tamriel think of the Akaviri they think of the Serpent-Folk, because one ruled the Cyrodilic Empire for four hundred years in the previous era. He was Potentate Versidue-Shaie, assassinated by the Morag Tong.

So we see that the Tsaesci are Serpent Folk. They came to look like men because they "ate" all the men of Akavir. the Tsaesci actually take on the characteristics of those they are able to eat.

The Akaviri Potentates of course were not eating men in Tamriel because that wouldn't go over too well with the populace, so they retained more of their Serpent like appearance as can be read in Carlovac Townaway's Last Year of the1st Era 2920 series of books. which gives very detailed accounts and descriptions as to what exactly the Potentates looked like, including a joust between The Prince and Potente Versidue-Shaie son. Remember, Tsaesci "are what they eat" they can take on human appearance if they consume a man/mer.

Now lets look at "Who exactly" invaded Tamriel during the Second Akaviri Invasion of the 2nd Era 572.

Kamal (meaning Snow Hell) is a nation of Akavir. It is inhabited by armies of snow demons (also known as Kamal), who thaw out every summer and attempt to invade Tang Mo, but are always successfully repelled by the monkey-folk.[1] Ada'Soom Dir-Kamal, a king among the demons, once invaded Tamriel, but was defeated circa 2E 572,

The Kamal differ from the Tsaesci as they are "Snow Demons". Snow Demons are not going to fight like dragons, breath fire, or try to imitate dragons. They are Snow Demons and have their unique style of fighting.

The Tsaesci were trying to "consume" the Dragons because they wanted to be like them. However, as we learn from The Blades, "Only a Dragonborn can permanently kill a dragon". The Tsaesci were unable to consume the Dragons on their own, they could kill them temporarily, but they were unable to consume them. They came to Tamriel searching for a Dragonborn because a Dragonborn can permanently kill a dragon, and this would allow the Tsaesci to consume them.

The Akaviri Dragonguard(later called the Blades) founding members were from these Tsaesci people that invaded Tamriel in the 1st Era 2703.

The Tsaesci do not fight like dragons, because they were unsuccessful in consuming the Dragons and taking on their characteristics. The fighting style displayed by the Tsaesci as written in books and taken from first hand accounts resembles nothing of what the DragonKnight purports as "Akaviri Martial Arts". The Dragonguard/Blades has never used such a fighting style in their history. The Dragonguard/ Blades are known for their curved Akaviri Longswords and "Far East" Samurai/Martial Art type of fighting style and honor system. The Blades never relied on magic, instead they relied on expert swordsman ship, unmatched hand to hand combat skills, mastery of archery, and skilled battlefield tactics which allowed them to defeat most foes and armies even if outnumbered just due to their expert skill in fighting.

So the Dragonknight claims or inference that they are using the Blades/Dragonguards fighting style is looking to be not true because the Tsaesci (Early Blades/Dragonguard) never used such a fighting style.

Is Every Dragonknight Dragonborn?

Well according to some of the descriptions, they are, such as the Earthen Heart Skill Line description:

The Earthen Heart Skill line is described as:

Draconic Power – tapping into their draconic bloodline, the Dragonknight can fortify their own defenses and lock down enemies, eliminating foes quickly and brutally.”

Draconic Bloodline....That sounds an awful lot like they are saying the Dragonknights are Dragonborn to me. According to lore a Dragonborn is one who is born with the soul of a Dragon. the Dragons themselves refer to this person being born with "Dovah Sos"(Dragonblood.) Dragon blood or Dragonborn are used interchangeably.

Dragonborn get many abilties, the most well known being that they can absorb souls of Dragons taking their knowledge and using it to master the Thu'um also known as "The Way of the Voice". Allowing them to speak like dragons do with words of power. When there are no dragons around to slay(such as the late 2nd, 3rd, and early 4th eras), Dragonborns can only learn shouts like everyone else..with decades of training. However Dragonborns have other abilities besides just devouring dragonsouls, such as Allesia's ability to dream of the future, Uriel Septim able to see the coming of the Oblivion Crisis, etc...so its not just limited to martial affairs.

Every Dragonknight being Dragonborn(having a draconic bloodline) is simply just not possible. Being dragonborn or having the dragon blood is a gift from Akatosh himself directly, and is not always chosen by heridary means as shown in The Book of the Dragonborn which was written by the Order of Talos (An arm of the Blades part of their loremaster archives)

Because of this connection with the Emperors, however, the other significance of the Dragonborn has been obscured and largely forgotten by all but scholars and those of us dedicated to the service of the blessed Talos, Who Was Tiber Septim. Very few realize that being Dragonborn is not a simple matter of heredity - being the blessing of Akatosh Himself, it is beyond our understanding exactly how and why it is bestowed. Those who become Emperor and light the Dragonfires are surely Dragonborn - the proof is in the wearing of the Amulet and the lighting of the Fires. But were they Dragonborn and thus able to do these things - or was the doing the sign of the blessing of Akatosh descending upon them? All that we can say is that it is both, and neither - a divine mystery.

The line of Septims have all been Dragonborn, of course, which is one reason the simplistic notion of it being hereditary has become so commonplace. But we know for certain that the early Cyrodilic rulers were not all related. There is also no evidence that Reman Cyrodiil was descended from Alessia, although there are many legends that would make it so, most of them dating from the time of Reman and likely attempts to legitimize his rule. We know that the Blades, usually thought of as the Emperor's bodyguards, originated in Akaviri crusaders who invaded Tamriel for obscure reasons in the late First Era. They appear to have been searching for a Dragonborn - the events at Pale Pass bear this out - and the Akaviri were the first to proclaim Reman Cyrodiil as Dragonborn. In fact it was the Akaviri who did the most to promote his standing as Emperor (although Reman himself never took that title in his lifetime). And of course there is no known hereditary connection between Tiber Septim and any of the previous Dragonborn rulers of Tamriel.

So we can see becoming Dragonborn and having the "Dovah Sos" is not a simple matter of heredity. So if Dragonknights are Dragonborn(i don't believe they are) then we have 500+ or more Dragonborns running around Tamriel at the same time during the Interregnum which just simply makes no sense, it makes no sense lorewise, it makes no sense for the Alliance War or any of it.

If Dragonknights have the Dragon Blood "Dovah Sos" as their descriptions seem to hint, then a Dragonknight could wear the Amulet of Kings and Light the Dragonfires, thus ending the Allaince War all together. Even just wearing the Amulet of Kings would be enough. Emeric, Ayren, and Jorunn would bow to anyone who was able to wear The Amulet of Kings because they would have proven without a shadow of a doubt that Akatosh himself chose that person to sit on the Ruby Throne. to elves, its acknowledgement Auriel has chosen this person.

The main reason the Alliance war is going on is because their isn't a legitimate Dragonborn Emperor. If Dragonknights are Dragonborn, then they can wear the Amulet of Kings which means they are legit rulers.

As for the Thu'um, the only people at this time period that know how to use the Voice are the Greybeards. The Voice Colleges were not started until Tiber Septim took the throne. So no one else knew the Voice, and the Greybeards are not going to teach the Way of the Voice to be used for martial purposes...the Greybards were willing to let Alduin destroy the world before using the Voice against him because it went agains their creed for pete's sake lol.

We also know that Dragon blood is not passed hereditary means. Just because a Dragonknight was related to a Dragonborn (a dad, grandpa, great grandpa, etc) doesn't mean he has the dragonblood or the ability to mimic dragons.

Perhaps the Dragonknights are actually Tongues?

Tonguesare individuals who have a natural ability to speak the language of Dragons - known as the "Storm Voice"[1], or simply the "Voice".

Tongues are typically Nordic in origin and those who demonstrate a talent usually require a great deal of study and training to develop their power. Nords consider themselves to be the children of the sky, and the breath and the voice of a Nord was his vital essence. Through the use of the Voice, the vital essence of a Nord could be articulated into a Thu'um,

Regardless of Race, even a Tongue, who is blessed with a natural affinity to learn the Voice, still takes YEARS to develop the ability...It t took Ulfric Stormcloak 10 years just to learn three words of Unrelenting Force and two words of the Disarm Shout...and these are more basic shouts, not the advanced kind like Fire breath (which you see Dragonknights use so effortlessly) which is one of the hardest shouts to learn and master.Even if the Dragonknights are Tongues, who is going to teach them? Because right now at this time period, no one but the Greybeards know how to use The Voice.

Conclusion

I am trying to get a better understanding of the Dragonknight itself. Its obvious to me from lore that they are not using an Akavir fighting style, because the Tsaesci never utilized this fighting style. The Tsaesci failed at consuming the Dragons, so they were not able to take on their characteristics or learn their secrets they so desperately wanted from them.

Please don't take this as a flame post, I am just trying to get an understanding of how the DragonKnight fits lore wise. The Templar is pretty easy to see, fits as priest, probably Stendarr, the Nightblade self explanatory, The Sorc same thing, but the Dragonknight doesn't seem to fit anywhere in lore and im hoping maybe someone can fill in the blanks with something that makes sense.