If they overhauled the magic system, then they could have easily expanded it to include the effects of Dragon Shouts, rather than simplifying it, which they almost certainly have done.
I mean the Shouts could turn out to be awesome, but at this point do we even really know what Dragon Shouts do? We only have a vague notion and I just don't see how Dragons necessitate these shouts.
They didn't "add in" shouts. Some Nords always had the ability. If you read the in-game books like Children of the Sky and the Five Songs of King Wulfharth you'll find information about the Shouts. Kind of interesting effects.
The breath and the voice are the vital essence of a Nord. When they defeat great enemies they take their tongues as trophies. These are woven into ropes and can hold speech like an enchantment. The power of a Nord can be articulated into a shout, like the kiai of an Akaviri swordsman. The strongest of their warriors are called "Tongues." When the Nords attack a city, they take no siege engines or cavalry; the Tongues form in a wedge in front of the gatehouse, and draw in breath. When the leader lets it out in a kiai, the doors are blown in, and the axemen rush into the city. Shouts can be used to sharpen blades or to strike enemies. A common effect is the shout that knocks an enemy back, or the power of command. A strong Nord can instill bravery in men with his battle-cry, or stop a charging warrior with a roar. The greatest of the Nords can call to specific people over hundreds of miles, and can move by casting a shout, appearing where it lands.
The most powerful Nords cannot speak without causing destruction. They must go gagged, and communicate through a sign language and through scribing runes
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Shor's Tongue
The first song of King Wulfharth is ancient, circa 1E500. After the defeat of the Alessian army at Glenumbria Moors, where King Hoag Merkiller was slain, Wulfharth of Atmora was elected by the Pact of Chieftains. His thu'um was so powerful that he could not verbally swear into the office, and scribes were used to draw up his oaths. Immediately thereafter the scribes wrote down the first new law of his reign: a fiery reinstatement of the traditional Nordic pantheon. The Edicts were outlawed, their priests put to the stake, and their halls set ablaze. The shadow of King Borgas had ended for a span. For his zealotry, King Wulfharth was called Shor's Tongue, and Ysmir, Dragon of the North.
Kyne's Son
The second song of King Wulfharth glorifies his deeds in the eyes of the Old Gods. He fights the eastern Orcs and shouts their chief into Hell. He rebuilds the 418th step of High Hrothgar, which had been damaged by a dragon. When he swallowed a thundercloud to keep his army from catching cold, the Nords called him the Breath of Kyne.
Old Knocker
The third song of King Wulfharth tells of his death. Orkey, an enemy god, had always tried to ruin the Nords, even in Atmora where he stole their years away. Seeing the strength of King Wulfharth, Orkey summoned the ghost of Alduin Time-Eater again. Nearly every Nord was eaten down to six years old. Boy Wulfharth pleaded to Shor, the dead Chieftain of the Gods, to help his people. Shor's own ghost then fought the Time-Eater on the spirit plane, as he did at the beginning of time, and he won, and Orkey's folk, the Orcs, were ruined. As Boy Wulfharth watched the battle in the sky he learned a new thu'um, What Happens When You Shake the Dragon Just So. He used this new magic to change his people back to normal. In his haste to save so many, though, he shook too many years out on himself. He grew older than the Greybeards, and died. The flames of his pyre were said to have reached the hearth of Kyne itself
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