The Galla Savages decimated the great Nation of Geri Kombe
Who are the Barsuugs I know the Usbiyahan are Darood and there several Cagdheer sub clans called Bah Usbayahan .
Marehan clan living near Harar
The Barsuugs are an old Dir clan that joined the Oromo confederation after suffering at the hands of the Egyptians and Habashis that came to control the Harar region. They are also mentioned in Futuh Al Habash as Barsub. As Richard Burton highlights, further down in the page you posted, all the Somali clans in the mountainous area of Harar are Dir or Darood with the exception of the Sheekhal.
The Marehan still live in the Hararghe area and even further inside the Oromo Zone. They are the remnants of an older Marehan presence in the Harar area during the Ahmed Gurey era.