The rewards seem to be randomly selected from a level-appropriate list when the leves are determined. As near as i can tell, you reset the leves currently available if you do one and turn it in. But if i remember right, thats different for crafting leves. With crafting leves, you get a different set of them available if you pick them up in town versus in the field. You mentioned ul dah leves. Did you check the leve handler in Scorpion Crossing(western thanalan)? Probly has a completely different list for you to look at.