Unlike the Mogu, we sleep. In-lore, the Shrine of Two Moons isn't a fortified military base full of troops and adventurers. It's full of exhausted refugees huddled together for shelter and warmth with, at best, a skeleton crew of guards. If Taran Zhu sent in the Wu Kao to kill everyone in their sleep, the Horde in the Vale wouldn't have stood a chance.
Also, if you spent any time doing the Isle of Thunder leadups, you saw how Taoshi assassinated a ship full of Zandalari, snuck us in past their sentry totems, assassinated the gatekeeper, and even Jaina and Lor'themar admit she did an entire army's work with just one adventurer's help.
And, yanno, grand job missing how Lorewalker Cho--someone who's life's work is recording and understanding history--even goes out of his way to point out after the battle at Serpent's Heart that Sha of the size and power we encounter had no historical record. We caused the problems in Pandaria by allowing Anger to drive the yaungol mad, Fear to corrupt the Mantid empress and force a swarm 100 years early, and the other five to infest the rest of Pandaria. We were the ones that empowered the Sha enough to allow them to infect the Temple of the Jade Serpent and the Shado-Pan Monastery. We are the villains here, and saying that we were decent enough to clean up our own messes doesn't excuse the fact that what we did was the equivalent of Crips and Bloods storming into someone's house, shooting each other over who gets to stay there, then calling foul when the homeowner threatens to pulp their heads with his shotgun.