Learn more about the Broken Shore on Wowhead:
Leading up to Legion, Blizzard released a series of animated shorts on Khadgar, Gul’dan, and Illidan. You can view these in-game as part of the Harbinger
achievement by finding books hidden around the world.
While Anduin and Sylvanas did not play major roles in Legion, mostly leaving the leadership to the various Order Halls, they are the focus of the Battle for Azeroth expansion. You can learn more about their styles of leadership, and clashes over Azerite and politics, in our recap of Before the Storm
Many players were sad that Vol’jin did not get a proper storyline as the Warchief, being appointed at the end of MoP and being fairly absent in the Warlords storyline. However, his plot continues in Battle for Azeroth and if you don’t mind spoilers, check out this article and cutscene with Princess Talanji