Tasks go in - order, if an | exists it means you can do those in any order, but have to all be done to continue on to the end. If tasks aren't listed in a chain, they can be done at any time.

Expansion Progression Quest Chain: Overcoming the Cataclysm - Not of This World - Answering the Call - The Bixies of War | For the Sake of the Forsaken - The Missing Scroll - Fourth Gate Investigation - Cautious Recruitment
Mission Quest Chain: Overcoming the Cataclysm - Not of This World - Answering the Call - The Doomscale Horde - The Defense of Lendiniara
Heroic Adventure Chain: A Helping Hand - Seeking Refuge - Protected Passage
Heroic Adventure Chain: Life After Death - Remember the Dead - The Other Brother
Mission Quest Chain: The Doomscale Horde - The Defense of Lendiniara | Xulous Prime - The Legacy of Bayle | Saving Jacyll | Houses of Thex - Hate Rising | The Fall of Lord Bayle | Burn Out - A Guide Beyond the Rift - The Journey Home