Nope. That's the number of paying subscribers. And if they pay, there must be something done right in the game.
Oh, there was. Too bad the old forums are no longer available. But the patch history is a little hint of the difficulty:
2.0.7 four weeks after launch: Black Morass, Durnholde, Shadow Labyrinth, Coilfang Reservoir and Mana Tombs nerfed
In addition to official patchnotes, following instances got hotfix nerfs: Karazhan (multiple times, on trash and certain bosses like Nightbane and Shade of Aran), Serpentshrine Cavern, Magtheridon (multiple times), Tempest Keep raid trash
2.0.10 eight weeks after launch: Botanica, Mechanar, Arcatraz, Shattered Halls, Serpentshrine Cavern, Shadow Labyrinth, Durnholde, Black Morass and Karazhan nerfed
In addition to official patchnotes, following instances got hotfix nerfs: Karazhan (multiple fixes), SSC (many), Gruul (many, on both bosses), Magtheridon (many)
And the big one almost exactly three months after launch which nerfed raid trash respawn time from 45 minutes to 120 minutes. The insane tuning of five-man heroics, Gruul, Magtheridon and SSC/TK raid trash caused more whine threads during first two months of TBC than LFR caused during whole MoP to date.