Meh, this will be a big weak point for the game, if I'm getting it correctly xD. It'll feel like if you want your story to overlap with your friends you need to do the mission or task several times before you can go on as a group, switching party leader each time. In worst case. or it's not possible at all to make a party group since every person gets a different reaction and so a different next task. Either way, playing together as a group through the storyline isn't (really) possible and you'll be moving parallel with your friends throughout the game, until you can all meet at the dragons feet.
The rest looks all great ofcourse. I expect no less.
It is supposed to focus just on you, not everybody around you. The truth is, the storyline is more like a single-player game aspect, and that's what they're trying to do. But if you can't tell, the single player events will also encompass what you perceive as story, as the events will be story-filled in my opinion. The events are designed to be the multiplayer storyline. Sure, it repeats itself, but it does it in a way that makes it seem more normal. Rather than how in GW, when you did the missions over with friends, you were repeating the exact same event, when it could also be like single-player content.
In GW2 we have single-player content that expresses only the player/team leader. They have the option to bring others along, but those people would only be doing that to experience a different storyline. While in the persisitant world, we have the multiplayer storyline, with the events and all. But they are also solo-able, to make it less restricting. And then, not to mention the dungeons, which probably incorporate some story-telling.
So we got three forms of main gameplay with story.
Main Storyline- Encompasses only the player and his story. You have the option to bring others along.
Dynamic Events- Encompasses the world as a whole. Can be done in a team, with other people but without a team, and completely solo.
Dungeons- Encompasses probably only the team doing the dungeons. Probably required grouping for these. Maybe some solo dungeouns.
I just hope the Storyline is as long as a Single Player RPG would be.