I did this quest last night, the first time as i approached Nehtlek'Vaa was over a hill and I saw health going down. When I got there he was dead, 2 Rebel scouts had killed him. I was unable to loot his corpse. A waypoint appeared for Collect Reward, but when I returned to Wilhalm it was obvious I had not completed the quest.
I chose to abandon it. I started the quest again.
Again he had been jumped and killed by 2 rebel scouts by the time I got to him. This time, I attacked one of the scouts (red to Rifles III) and she chased me rather stupidly all the way to the Imperial Outpost just up the hill from Bestine. She of course got blown away by the Stormtroopers there, I was able to loot, but didn't seem to get anything.
However later I noticed I did actually have a data disk in my inv, went back to Wilhalm and the quest completed.
I guess from all this you are either meant to protect Nehtlek'Vaa or else he always gets killed by the scouts and you are meant to kill them.