Mists of Pandaria is the story of an outsider, washed upon foreign shores, who changed the course of destiny for herself (or himself) and the world entire. Pandaria and the rest of Azeroth shifted on the fulcrum he (or possibly she) provided - the mogu, the mantid, the sha all fell before her (him) and even the Thunder King himself lies dead at his feet... or hooves, perhaps. Also, it hay have been her feet. Because in the end, Mists of Pandaria is the closest any MMO has ever come to being a single-player campaign and an multi-player experience at the same time. Mists of Pandaria is about you, your choices, the impact you have had and will have on the world.
There have been tragedies. This isn't about those tragedies or what they might mean in the larger picture. Gods and dragons and celestials can worry themselves about what may be and what might happen - heroes live and act in the now. Given a bad situation, they take action to make it better. It can hurt, absolutely, but finding that balance between contemplation and action, to know what to do and then to do it, is all the difference. Let's tell that story, of one figure who landed a vagabond on a new shore.
There will be spoilers for Patch 5.4 and the legendary quest chain in this post.
The Klaxxi, for instance, tell you the story of Y'Shaarj, the sha, and the mantid, including the Klaxxi themselves and the traditions of the Empress. They believe firmly they understand the lessons of history, that they grasp the narrative that is unfolding as they oppose Grand Empress Shekzeer... and they fail. It is not the Klaxxi who ultimately storm the Heart of Fear and free the mantid from the domination of the Sha of Fear, not the Klaxxi who are responsible for the continued existence of the mantid people. Despite the story they tell you (a grand, sweeping epic of untold thousands of years, of mantid honing their people using the pandaren as a whetstone, of the long service to the gods that are their gods) it is not and never was the Klaxxi or their paragons that save their people.
It was you. You saved them. You stormed the Heart of Fear. You drove the Sha from its puppet Empress, leaving the cycle free to repeat itself, with a chance to repair the horrific damage to the Kypari trees and start again. If the mantid endure, it will not be because of the Klaxxi. They failed. You succeeded.
Similarly, the August Celestials see in your an instrument to a grand design, and perhaps it is so. Your arrival in the Jade Forest did help bring about the great conflict between the Alliance and the Horde that toppled the jade serpent statue and prevent Yu'lon's return to the cycle of death and rebirth - and had you not done so, all that followed would not have been. Who can say? The Celestials may in fact be right, but it's hard to tell - they share only so much, after all. But it was you who stood not once, but twice against the testing of the Celestials and emerged victorious. It was you who learned the lessons of each, and incorporated them - you who walked up the mountain with Shaohao's shade and listened as he, too, told you a story of the distant past and the great error he made in purging all doubt, fear, anger, violence, hatred and despair, but retaining his pride... his hubris in thinking he could solve all his people's problems in one act, that his people could forever isolate themselves from the world.
And yes, you made mistakes along the way. You didn't always stop great calamity from befalling the new land you found yourself embroiled in - the destruction in the Jade Forest attests to that, as does the presence of the Horde and Alliance in the Krasarang Wilds. You brought your world with you, brought your war in your track. The end of stasis is often the move violent for the period it was held in abeyance. You made mistakes, but you also proved yourself - you stood against the Thunder King and his mogu and brought Lei Shen low, ending his story of the rise of his people and the rebirth of his empire. He, too, thought he knew your role in the days to come.
This is why it's fascinating, once you overcome the final test of the August Celestials on the Timeless Isle, once you assemble the proper materials, and present them to Wrathion you get more than just an item of power. Indeed, you get far, far more. You get a much better present than the magic Wrathion promised you - you get a story. Your story, told to you by Wrathion and Lorewalker Cho, and at last you get to see the most unreliable of all narrators describing your own life to you. And it becomes clear that Wrathion, too, thinks he understand what has happened and what will happen, that he sees a role for you in the future and believes he has destiny all mapped out, plotted, plucked and shaped. Lorewalker Cho demurs, finding Wrathion's choices of words at times disturbing and contrary to the lessons he sought to teach you, the two of them becoming like their very stories themselves battling for dominion over you, and what is to come.
But it isn't their story to tell, ultimately. It's yours. It won't be Wrathion, or Cho, or the Celestials, or even the Klaxxi or the King of Stormwind or the Darkspear tribe who tell this story. They may be there, but the story isn't about them, not any of them, just like it's not about Garrosh Hellscream or Y'Shaarj's dead beating heart, or the Shado Pan or the Golden Lotus. They're in it to be sure, but it isn't their story. It was the story of a lone adventurer who came to a new land bringing the whole world with her (or again, possibly him) and who changed everything.
Take up your cloak. The Vale is shattered, destroyed. The world is stunned, aghast at the perfidy of the mad Warchief. Celestials and dragons and gods can only watch now. Now is the time for heroes.
Now is the time for you.
Tell your story.
While you don't need to have played the previous Warcraft games to enjoy World of Warcraft, a little history goes a long way toward making the game a lot more fun. Dig into even more of the lore and history behind the World of Warcraft in WoW Insider's Guide to Warcraft Lore.