What other MMO has done this, and why does SE think it's a good idea?

[Jinko]

As an existing player it makes sense that the story continue but if I came in as a new player and someone told me I had to play through all of the old stuff that no one is doing before I can start the current stuff I'm going to be less inclined to even try the game out. I don't think most people would like to be stuck perpetually playing catch up which is what is bound to happen to newer players as the number of expansions increases.

This is very true, however I doubt it will be as bad as all that, this dev team have made a point of keeping old content revelent with roulettes so I doubt new players will have a problem completing old content.

The thought of having to do all that story content though makes me head spin, I don't envy new players, especially as much of it is running and teleporting around like a idiot on a fools mission.