You can tell if you won't get xp if the quest in your log is gray-colored. Ditto for a foe's level in the targeting frame. Alderaan has a bonus series that starts around 36/37, so you could go do those. Go in Castle Organa, bottom floor, second or third room on the left side of the main hall. You'll see the quest icon on minimap as you get close. They have a few heroics and stuff that will definitely be a challenge, plus normal missions for around 36-40. You do missions for Jace frickin Malcolm himself! I guess he's cleaning up Alderaan after he wiped out the Imps in the "Hope" trailer.