It's about time to add Coil story mode, isn't it ?

[Airikay]

MMO usually fail when they catter to hard to once side of the player base totally ignoring the other or when they never decide what to do. And I have high doubts a MMO would fail because of "no rewarding end game" alone. there are MMOs without any relevant endgame and still going.

You really should look at the rise and decline of WoW. The highest growth of subscription rates for WoW was during original vanilla and BC when in fact most of the content was closed off to 99%. Even though it was closed, it kind of kept a goal. With WoTLK it peaked around Ulduar which was basically the birth of normal and heroic. Through the rest of WoTLK sub's stayed about constant and with Cataclysm it started to nose dive as they streamlined all the content. If a game doesn't have a certain amount of difficulty it has no replay value and becomes one of those one day games instead of something that needs to be continuously worked on. With no endgame, not only will raiders lose interest but also most everyone else that doesn't use the game as just a chat service. With no substance every server except Balmung will be a ghost town.