Which mission has the highest energy/experience ratio?

the dark theft is one of the highest at 12:1

But if your looking for normal missions that don't require npcing, the prejor chain seems to be pretty.good.

If my information is correct, these are the missions with a 3.0 and higher XP/Energy value.

The top three:
1) 13.0 -- The Zolazin Battle (3rd mission in the Zolazin chain)
2) 12.0 -- The Dark Theft
3) 5.0 -- Dynite Shortage

The first four missions in the Prejoran chain (min rank 40):
4) 3.6 -- A Visit to the Homeworld
5) 3.3 -- Mysterious World
6) 3.2 -- The Slave Revolution
7) 3.0 -- The Prejor

Other missions (tied at 7):
7) 3.0 -- Aerlen Field Training (Aerlan race starter mission)
7) 3.0 -- Audience With High Council
7) 3.0 -- Finding the Fornyis Twins (3rd mission in the Terran Outsiders chain - min rank 75)
7) 3.0 -- Konqul Initiation Ritual (Konqul race starter mission)
7) 3.0 -- The Colossal Project (2nd mission in the Planetary Project chain - min rank 50)

The starter missions are low total XP. If you change races they are quick and easy to get for the mission completion rewards.

The average is around 2.3 (not counting the seasonal or any from the latest daily The Uninvited).