Visions of Danger

So if you're like me and you're coming to do this quest well after BFA and you're absolutely confused by the requirements, the fact that they've changed them, some guides are outdated, and the comments here are seemingly contradictory, and you just want your damn tauren heritage armor and you get to the point where this quest should be offered and it isn't:

The problem is that you can be sent to Nazjatar BEFORE you advance the war campaign enough. And that Blizzard has changed the prerequisites for this quest multiple times.

So here's the full list of achievements and quests you have to do to get to the point where Visions of Danger is offered:

You need to complete Ready for War. This is the 8.0 war campaign achievement.
You need to complete Tides of Vengeance. This is the 8.1 war campaign achievement.

Tides of Vengeance will end with the quest to send you into the Siege of Darza'alor.
You do NOT need to complete the quest to do it. Nathanos offers it, but it is not required anymore.

You DO have to go to Nathanos to complete The King's Death, however. This seems to be where some of the confusion lies - The King's Death (and the following one: The Return of Derek Proudmoore) is NOT needed for the Tides of Vengeance achievement (and to unlock Nazjatar) which makes you think you're done with the 8.1 campaign, but they ARE NEEDED to start the next part of the war campaign to be able to start Visions of Danger.

Once you complete The Return of Derek Proudmoore, go see [npc=150433], who is standing at the north end of the dock Nathanos' ship is at. She offers you Righting Wrongs which begins the 8.1.5 war campaign quest chain. Once you have completed:

Righting Wrongs through Under False Colors (you only have to start the follower mission mentioned, not complete it)

and then

Securing Warfang Hold (offered by Nathanos immediately after turning in the previous quest) through A Display of Power, you have advanced the War Campaign far enough and can return to Nazjatar.

If you have completed all of the above *and* advanced the Nazjatar campaign up through arriving, opening the portal back to Zuldazar, the side trip to help Magni and MOTHER and Ebonhorn, introduction to Benthic armor, and have completed Down Into Nazjatar, Lor'themar will have Visions of Danger to give you.

(I actually completed well past Down Into Nazjatar due to some outdated information until I realized I had not done the 8.1.5 questline as indicated above, but you shouldn't have to.)

I really genuinely cannot stress enough the addon BTWQuests to help you keep track of where you are in the chain and what you have yet to complete. I also really genuinely cannot stress enough that Blizzard really, *really* needs to remove all of these questlines from allied race/heritage armor unlocks.

You have to finish these quests in order to complete Clearing out the Cache. After, you will get Visions of Danger in Newhome.
1. Create Your Own Strength
2. Settling In
3. Scouting the Pens
4. Save A Friend
5. Becoming a Friend
6. Down Into Nazjatar
7. Insight into Our Enemies
8. Deteriorating Knowledge
9. The Price is Death
10. What We Know of the Naga
11. Scouting Undercover
12. Sating Snapdragons
13. Working with Purpose
14. Stealing the Naga's Secrets
15. Sea Slug Liquidation
16. Coveted Crystals
17. Let the Residue Lead You
18. Clearing Out the Cache

This quest didn't pop up for me despite having completed all the quests required for this - or, at least I thought I had. Turns out you need to complete the previous war campaigns, which means completing the raid quests. I hang my head dejectedly...