How many of those players are on the US/EU realms, as opposed to the asian ones (that very few people on the site will ever encounter) where it's rather likely having a couple of dollars of game time is counted as an "active" account by Blizzard? Not that people playing on EU does you any good at all if you're in the US, and vice versa.
WoW is not doing "fine". WoW is still profitable to the developers, but the number of ghost realms where pugging a raid is all but dead is at an all time high, because of however million actual players there still are, they're spread across more servers around the world with region barriers than there have ever been. It makes me wonder if people are deliberately being incredibly dense about this with so many people saying "oh shit, my realm is dead", or just quitting because encountering strangers in their online fantasy game has become so uncommon that it's souring their view of the genre. Even better that, though they may not be able to form a group in trade to achieve anything, they can still venture out into the open world and maybe encounter *someone* around the same level questing from another realm, if they're playing PvP they'll sure as hell be able to encounter some level 90 douchebag patrolling said lower level zone looking for people to kill and camp.
The game is very literally falling apart at the seams. Some are still playing on the super realms, and they don't notice the decreases so much, because as one person quits the game, another gets sick of their dead realm and moves over to replace them (or near enough), and the new realm mergers will patch it up for a while. However, sooner or later you'll be arguing "WoW still has 5 million players", again even though that might mean 1 million max still playing in your entire region, let alone their activity levels. Then perhaps at 2.5 million "it's still about the same size of all it's rivals", not that it'll help your once swarming server form a pug.
The game needs a drastic revamp and with more content for casual players. The best thing for it right now would be getting rid of the idiots who get upset about casual players walking around with epics 40 ilvls lower than their own. Just let them identify themselves by whining on the forums, then ban their accounts. It'd be brilliantly easy, ban the one and his loudmouth friends would identify themselves sulking about it. 20,000 less self-important elitists and maybe new players might start encountering nicer people in their random dungeons and making friends, instead of not bothering to talk due to previous bad experiences.