You really believe that Diablo III is a loss leader that simply bleeds money and makes none? You think nobody buys the game anymore? The expansion didn't sell? Another one will never happen? Maybe you could explain the recent $15. Necromancer that I'm sure has sold like hotcakes across multiple platforms and which I bought myself. Also, Activision is calling the plays ultimately now and they are not in the habit of giving away anything. In short, Diablo III makes money and no doubt more money making is planned or Diablo III would not exist because no matter what Blizzard might want, Activision is calling the plays now. When I see Destiny using Battle.net and being wedged in with Blizzard's titles I am inclined to think Battle.net is an asset at Activision's disposal even without reading a bunch of stuff I don't care about related to all of that. If Battle.net is at Activision's disposal, it follows that everything Blizzard is as well so far as top management is concerned.
Diablo III is just another example of a popular game many people like that is sustained by that and nothing else. Need more money? Give them a new class they want, some virtual toys to go with them and watch the profits come rolling in 15 bucks at a time over a huge number of players.
Edit: cut out the EQ and John Smedley story. I'll save that for another time but it is related to this discussion.