uh, stable subscriber numbers were (by far) the largest during WotLK? It has the highest rated raids and 5 man dungeons, even pvp and 'open world' is highly regarded in WotLK. Class balance and development was very good, did the game become more 'friendly' and in some ways mark the start of the downfall? Maybe, I think that was Cataclysm (end of cata).
http://powerwordgold.blogspot.com/20...2005-2013.html
Subscriber numbers are obviously not alone a indicator of how good a game is, but to hold and not lose any subscriptions at those numbers is impressive.