I have found a good "rule of thumb" for FFXII to match the level of the guest in your party. "Lamont" was level 13 on Lhusu mines, right before the Leviathan mission, so you should have been at least 13 to finish Lhusu. And 18 to get to the Sandseas (after Leviathan).

Considering you did beat the Ba'ganman guys and finished Lhusu at level 9 you must have some good tricks up your sleeve. Care to share them ?