I haven’t done that quest yet, but since the 1.2 patch the Raiders quest seems to have been fixed.
I just had this problem last night. I may reload my save from after the main story line and wait a couple in game days to see if the waypoint pops back up.
Had a similar Problem with the Kuman Raiders.
Because of the Maskarade Quest from Andreas I raided 3 Kuman Camps before opening the Kuman-Raider quest.
So i had already 3 Helmets
First 2 Kuman Camp quests where two i havnt raided yet. So were working.
The third i already raided and finished this quest in the dialoge menu already.
The forth-camp: i raided i already, went back and well -> No one there
I waited several days and still, no one there.
Several Days later - while i was deer-hunting i spotted Kumans in the Forest. “Did they Respawn?” i asked myself. Killing them… “oh it was the neighboring camp” - but to be sure that it is bugged i went to the waypointed camp. There where new Kumans, i killed them, no Leader-helmet. “Damn it.”
So i went further, at the moment i had the music silent and turned the volume up to hear the dear… but instead i head silent hungary screams. “did i forgot someone?” I went back to the camp. One Kuman stand there, i shot an arrow - but he survived and run. Followed him through the forest until i got a good shot on him. - it was the leader… he respawned.
I read somewhere that if you bee in prison for 10 days all NSC would respawn but i wasn’t in prison. Maybe letting some day’s pass would be enough?
same issue, quest given, no journal entry, no markers. anyone know which direction to go from talmberg at least?