They say that people will listen to you and remember what you have to say more, if you put it into a nice story. That's what I did in the last post. While I am certain that most of this is at least roughly correct, I am also certain that some of it is wrong. Anyway, time for a dry quintessence.
World of Warcraft's growth rate went from a perfectly stable 2 million subscribers per year during 2006 to 2009, to zero during WotLK. This was exactly the time when Blizzard changed the character progression mechanic.
The old mechanic allowed players to explore (mostly) static raids at their own pace. Raid groups could take their time to complete the content. Since 'better' raid groups progressed faster to more difficult content and without as much equipment, they faced more difficult challenges than 'not so good' raid groups.
The new mechanic forced all players into exactly one raid tier. They had a specific amount of months to complete it, before it became obsolete from a character progression point of view. The challenge level was the same for all players. Heroic raids were insignificant, as, for various reasons, they were visited by only a handful of players.
The old mechanic did not encourage players to visit dungeons once a day. And although forming a group on their own was often tiresome, when players did visit a dungeon, it usually was a pleasant social experience. Moreover, dungeons mostly weren't boring, because players didn't visit them all that often. Dungeons had different challenge levels and required different amounts of time to be completed.
The new mechanic strongly encouraged players to visit a randomly chosen dungeon once a day. They completed this dungeon within an anonymous group of other players they would never meet again. Players ran dungeons so often that they very soon found them very boring. All dungeons were adjusted to have the same challenge level and to require the same amount of time to be completed.
The old mechanic used 'random loot' that made badly-geared players gain gear very fast, while well-geared players gained gear very slowly. Most raid dungeons never became obsolete, because there was always something someone would still need. Generally, loot was given out more slowly and often became infamous.
The new mechanic used 'badge loot' that made poorly and well-geared players gain gear at roughly the same speed. All, but the current raid dungeon, were very soon obsolete from a character progression point of view. Generally, loot was given out much faster than before and was usually forgotten fast.
The classic-TBC mechanics offered reasonably tuned content that players could tackle in a pleasant social environment and at their own pace. Sure, players moaned and complained about those who had more: The unemployed, the students, the born-rich. But at the end of the day they had fun when they played in the evening. And thus they stayed subscribed.
One complain about classic-TBC was that most players never experienced the end of the story. I think this is a very legitimate complain. I think it encourages us to think about separating the overarching story from the raiding. Alternatively, raids could be transformed into leveling dungeons when an expansion hits, or the balance could be tuned carefully to ensure that eventually every raid group overgears the next raid in a way that anybody, who invests enough time, sees the end of the story.
In the absence of such a solution, the question is what is more important for players? To experience the entire story or to always have reasonably challenging content that they can do in a pleasant social environment at their own pace?
It's a hard decision, especially for someone like me. But if I ran a business, I'd chose the content over the story. Players just care more about whether they can have fun this evening, than whether they will experience the end of the story in two years.
In classic-TBC, one complain of advanced raid groups was that the system made it often hard to replace players. I think this was a concern of a minority. Recruitment-runs in older raid dungeons and advertisement of advanced raid groups in cities actually enriched the game and gave new players a feeling of 'everything is possible'.
I do think that classic as well as TBC should have had more introductory dungeons and raids.
When the new mechanic was released, the players were busy fighting shadows and didn't understand that WoW had neither become too hardcore nor too casual. It had become a one-size-fits-all that couldn't satisfy the broad spectrum of 12 million players.
Most ironically, the new system was in direct contradiction to the intend of the developers to cater to all players. Maybe the developers were fighting shadows, too?
Edit: Seanas just sent me a really good link. It's from Summer 2009.