I don't know the author and his gaming background but he certainly hasn't spent much time playing blizzard games. At least he isn't a 'hardcore' gamer. Truth is, if you are a casual gamer you probably won't notice how dumb their current development is.
In short: WoW: Numbers don't lie. People would still play mmos if there werent any worth playing. http://www.mmo-champion.com/content/5063-WoW-Down-to-5-6-Mil...
Diablo: Current content is shit, multiple design failes that needed to be corrected. Both D3 and the addon weren't ready on release, needed patches to correct the bad quality.
Hots/Hearthstone/Overwatch: Knockoffs of Dota/LoL, Magic, Team Fortress. I don't think a knockoff should be called a quality game. Also, both Hots and Hearthstone have/has horrible balancing issues => bad quality considering being balanced is the core content of the game. Not to mention that Hots was really shitty from a technical pov (after beta).