An example of a game with a coherent narrative system that doesnt feel like a slog is the original Guild Wars.
While it has its own flaws, its msq progression was "Go to this story dungeon and run it", because EVERY dungeon was a story dungeon. You could do all the side quests to get money and XP and lore, or you could run the dungeons back to back to back (minus the travel time which also had you exploring its worlds) in short order and get to the endgame first and explore later for all the stuff you missed.
I have a friend who just beat Shiva hard for the MSQ last night. He's 62 or 63 now. Just wants to get to the point where he can run actual content with us without having to spend 70 canadian fakebux to skip most of it. He hasnt picked up a single side quest. Its been a rather awful experience. He finished his free time and is having to debate if the sub is worth it.I mean the problem is not even the MSQ as a whole, but the fact that if he actually wants to enjoy even the optional content, he has to complete the MSQ no matter what, doesn't matter if he has the level for the other stuff, he cannot even prepare himself gearing up because he can't spend his mendacity. And that guy did not "farm", he only did his leveling with us for fun - just so we can actually have something to do together - and ended up getting to 70 before even starting stormblood.
The argument that with new expansions people rush to endgame is a good argument... for removing MSQ from dungeons, trials, raids and the like.
Let people experience the MMO content they want to experience in an MMO (like crafting, gathering, raiding, dungeoning, hard content'ing), and do the lore heavy (or sparse) single player slog experience on their own time.
Yes, people expect things in modern MMO's like multiple at level cap dungeons, multiple raids, and multiple side progression paths, at release, in every new expansion. Having those things is how you justify the box prices of subscription models.