"Shadows of Kul'tiras"
Jaina returns to Kul'Tiras to do whatever(recruit troops/take over/cry), when she gets there she finds it under attack by Old God-corrupted Zandalari Trolls.
During a brief armistice between horde/alliance, the Alliance goes to Kul'Tiras to help defend, and the Horde to to Zandalar to kick OG Troll ass and cut off the flow of troops to Kul'Tiras.
Tier 1 - 2 dungeons on on Kul'Tiras and one on Zandalar and a OG Troll raid.
While we are off dealing with that shit, Azshara sneaks into Silithis, Drinks the Titan Blood, gets super swole - queue Naga invasions all along coastal EK and Kalimdore shores.
Tier 2 - There is a Naga/Azshara raid and maybe some OG/Naga dungeons... Underwater dungeon place 2.0.
After we kill Azshara, Titan Blood infused/resurrected OG's break free and ravage our capitols.
Teir 3, Old God raid where we fight ALL the Titan Powered OGs...