After completing the Main Story Quest to defeat the Tempest, the quest series may appear to be over when you turn that quest in, but it actually picks back up again if you take “Strider of the Sands,” available from either Great Cleave, Shattered Mountain, or Ebonscale Reach.
After you’ve given yourself the Desert Cerate, you can enter Brimstone and then the Brimstone Main Story starts on the character “Ghazi” after you turn in ‘Strider’. Let me know if this doesn’t work for you.