What? Every non-combat single quest, MSQ or otherwise is carried out solo. With a handful of exceptions, every piece of MSQ combat content can be carried out solo.
If you really believe that "solo play in a world of other players" will destroy 14, sorry to tell you, but that's already happened.
To your point below:
This is simply not true. Most of the significant events appear in cut scenes. When there are raids/dungeons/trials associated with those events, 98% can be carried out with NPCs; that is, solo.