You're stating that Blizzard needs to differentiate between apples and oranges. I'm stating that it doesn't matter, because subscriptions are just a scapegoat, a number to make players feel proud and important. No real investor would pay attention to subscriptions.
Just to make things clearer, here's an example:
Say your friend comes to you and asks you for $100. He says it's for a good investment, that he's developing a mobile app or something, whatever you want to make up, and promises to pay you back DOUBLE what you loaned him. Now you know your friend, you know he's trustworthy, blah blah, so you cut him a check for $100.
Two months later he comes back and gives you TRIPLE what you invested him. He says that his app was better than he expected, and he reaped more than he thought that he would. Would you then start demanding that he give you explicit details of how his app sold? Would you want to know how much people paid for it? Would you ask him how much of that was selling advertisements in the app? If his app had a premium and a free option, would you demand he break it down for you how much of each he sold? Or would you just be happy if he told you how much he had earned off the app?
All an investor cares about is the money. They don't care about finicky details that are defined by the corporation. They don't care whether it's a premium account, or a bonus account, or a collector's account, or a free account. They just care that their investment is returned and that the company they are investing in is boasting solid profits, etc.
It's a loose example, I know, but I hope it just pushes across the point I'm trying to make. Money is money, profits are profits. Ignore the little number called "subscriptions" for a bit, and just focus on the fact that WoW has been and will be, for awhile, the most financially successful MMORPG of all time.