The trap of linearity
Tobold is experiencing Mists of Pandaria largely spoiler-free, and is concerned that MoP is shaping up to be just as linear as Cataclysm.
Blizzard is making most of their money from people like my wife, who was subscribed to WoW all the way through Cataclysm, and was busy leveling alts.
Mists of Pandaria might well turn out to be the worst expansion ever to level alts in. It has the linearity of Cataclysm zones, but where Catalysm had two possible zones to start in, Mists of Pandaria only has one. The Jade Forest might end up being more hated than Hellfire Peninsula, because in Hellfire at least you could skip the quests you didn’t like. All the talk you heard about Blizzard making MoP more casual-friendly is going to come to nothing if those casuals become bored of leveling alts due to linear questing.

This is exactly the problem I encountered with SWTOR. The class quests are unique to your class, but the rest of the zones are incredibly linear, with very little room for deviation. The best you can do is try to get ahead on XP and skip side quests, but you can’t just ignore a
This pretty much killed any desire I had to play alts in a serious way in SWTOR, despite my interest in the different classes and their individual stories. It is, I think, probably the single biggest flaw with SWTOR: the replayability is very low1, which means that there’s little motivation to continue subscribing2 after you’ve played both factions to level cap. Even raiders need something to do outside of raid times.
Tangentially, The Secret World has the same problem — however, it’s less of an issue in TSW because you can do everything on one character (except experience the very small amount of faction-specific content), so a) there’s less impetus to play alts, and b) you’ve got a lot more to keep you busy on your main character anyway.
Totally linear quest progression is, I think, a design mistake for a traditional MMO. It may enable the devs to tell more interesting, engrossing and epic stories, but it’s at the expense of replayability, and replayability is where the MMO money is.