The latest story requires 5-10 man instanced content in order to complete it. Anet has not required group content for story since the original Zhaitan fight which they later changed to be soloable.
Making group content required for the story is a step backwards.I prefer my first playthrough of new story content to be done solo so that I don't have the distraction of another player. Now, not only do I need another player, but if my friends aren't online and willing to do it with me I am stuck with randoms who are even more of a disruption to my enjoyment of lore and story.
I know Anet wants to push players into trying out strikes but this is not the way to do it.A chapter in my story journal should not require group content.
Edit for some clarification:
I am still really happy with how everything else was done in this release. I do play group content all the time. Story has just always been a thing that was solo, and I enjoyed it that way. I liked to be able to play through and absorb the new lore without worrying over getting a group together or the chance of getting a troll. And I will be playing this content. I will probably enjoy it a lot, but I will still always prefer story stuff to be solo.