I really, really hope that the Main Quest is forced solo, personally. I think this game is almost completely group stuff already, we need so hard and challenging solo content as well, not a LOT but a little, and the main scenario is exactly the right spot for that.

AND, also, I really do wish there is a 'DoL/DoH Main Quest' as well. Despite not beign a crafter myself I think that one of the greatest addition to the MMO genre that XIV has done is all the focus it gives to the crafting and gathering classes, and it would be incredible to see them have their own questlines, as in, full-blown questlines.