So, for other fellow completionists... I was trying to get this quest variant yesterday with no luck. From what I gathered, there are 2 variants of several quests.
First you want to start regular zone quest chain, starting with Falling Down.
You continue Dread Wastes quest chain until you stumble upon Extending Our Coverage offered by Kor'ik. At this point, you would normally follow quest chain with Kor'ik as your questgiver. This is version what 99% of players does:
Extending Our Coverage (variant A)
Crime and Punishment (variant A)
Better With Age (variant A)
By the Sea, Nevermore (variant A)
If you want to unlock alternative quest chain (quest objectives are the same, but quest ID differs) then DO NOT ACCEPT Extending Our Coverage from Kor'ik. Instead, you have to finish Dropping Our Signal and follow-up Corruption Runs Deep. In this quest Kor'ik, your quest giver turns traitor and is killed. After completing this quest, there is different quest chain offered by new quest giver Zer'ik.
Extending Our Coverage (variant B)
Crime and Punishment (variant B)
Better With Age (variant B)
By the Sea, Nevermore (variant B) -YOU ARE HERE-
However for some reason, even that I did first 3 quests on variant B, my last quest offered was By the Sea, nevermore (variant A). Not sure if I misunderstood principles I described above, or quest is bugged and By the Sea, Nevermore (variant B) is currently impossible to complete. If you found the way to pop this quest, please share your experiences below! Hope this helps someone at least for first 3 quests.