Important to those whose Heroes lived. Important to Thedas, what with all that is going on with the Wardens, Morrigan, the Blight, the Black City, Ferelden, etc. The Hero's character ties into all these things.
Which means she is buried in her own personal tomb at Weisshaupt Fortress, which is where the next installment might take place. That means you would get to see your Hero's final resting place.
The default world state is for BioWare only. It has no influence over any player's world state.
No, my response is the same as it's always been. You can have the Orlesian Warden or not depending on what you want. The Orlesian Warden would not replace the Hero. For example, he or she can't replace a Hero who romanced Morrigan or had a child with her. No, the Orlesian Warden would just be a decent substitute who could fulfill the basic roles, but not all of them.
The 5th Blight is where the HoF was important. The very fact that you can play the game exactly "right" all the way to there, and still die demonstrates that that's where the Warden's importance to the story ends. Awakening shipped with it's very own protagonist, just in case.
Events in Weisshaupt currently do not require the HoF to take place, at all. In fact, those events could happen if the 5th Blight never happened. Assuming my DE's ashes were sent there, instead of back to her clan, then yes, I could see her final resting place. However, that implies that she's more important to that story dead, doesn't it? Living characters don't usually have final resting places.
The default world state is for BioWare, however, since their canon is a female DE that took the US, beyond the story of Origins, the HoF just wasn't all that important. Otherwise, they'd have had a live HoF to build off of in the future, if that's what they wanted to do.
Since the HoF can be so readily replaced for the story of any DLC or game, they aren't all that important. That's the flaw with this argument: You can replace them with Random PC 875, and still get the same story. You see, they have to write for a dead HoF too, it's a possible ending to the game, and as we can see, OGB wasn't Thedas shattering after all. I imagine BW thought that that "loop hole" would be a lot more popular than it was, but all one needs to do is snoop around the Legacy forums for threads about the DR to see that it really wasn't. Some were even mad that a romanced Alistair could
swoop in and steal the Archdemon kill.