I think what you are talking about was the World of Warcraft Infographic which was released in January of 2014.
Link: http://media.wow-europe.com/infograp...fographic.html
At that point it was over 100,000,000 people had tried it (including trial accounts) which is just gobsmacking if you think about it for more than two seconds. The whole infographic is pretty interesting.
Yes, churn has always been high. Well over 90% of everyone who has ever given the game a look have quit. That makes these threads which attempt to pin the issue on one thing mildly ridiculous. It's the way of things.