You know its really funny. About 2 months ago as they were announcing that the Firelands would be delayed, Blizzard made the statement that people were moving through the content slower than expected so they were pushing back the release of Firelands to 4.2 and allowing ZG and ZA to help make the current tier easier.
Now Blizzard is saying that people are going through the content faster than ever. Completely contradictory to their previous comments.
Which one is it? Sounds like alot of corporate bullshit to try and appease their investors. My guess is a large portion of the 600k who quit probably felt that the game no longer suited them either due to difficulty or massive amounts of changes.....
Theres still only a few hundred guilds worldwide who have completed this entire Tier. Those 600,000 people have nothing to do with them.