It All Makes Sense Now

The Legion pre-launch event includes the achievement It All Makes Sense Now.

Simply talk to [npc=112198] in Stormwind City, or [npc=112527] in Orgrimmar in order to obtain the various pamphlets.

For convenience I have compiled a list of the NPC locations in both cities:

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• Stormwind City
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• Orgrimmar (Cleft of Shadow)
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Note that (at the time of writing) there is a collective cooldown around 15 minutes. Simply pick one NPC, collect the pamphlet, do not delete the item, wait, then talk again to receive a new pamphlet. Since the items are unique, keeping the old items guarantees you won't receive duplicates.

Have fun preparing for Legion! :)

*Edit* So apparently people are killing themselves to buy-pass the timer. As long as this works, you can use the following code to help automate releasing your spirit, accepting the spirit healer ressurection, and clicking the button for the pamphlet:
/run IAMSN=IAMSN or CreateFrame"Frame"IAMSN:RegisterEvent"CONFIRM_XP_LOSS"IAMSN:RegisterEvent"GOSSIP_SHOW"IAMSN:RegisterEvent"PLAYER_DEAD"IAMSN:SetScript("OnEvent",function()AcceptXPLoss()SelectGossipOption(1)RepopMe()end)
Copy the code above and paste in chat. Once done, simply log off and on again, or reload your interface using /reload

Considering the achievement is a feat of strength, if you wish to track it you can copy and paste this in chat:
/run AddTrackedAchievement(11065)

***NOTE: This achievement can be fast-tracked by repeatedly killing yourself and resurrecting! See below for details***

This achievement will be available during the Legion pre-launch event.

To obtain it, speak to any of the various [npc=112527]/[npc=112198] NPCs during the event, scattered throughout Orgrimmar (14 total) and Stormwind City (16 total).
The pamphlet you get will be random, regardless of which NPC you choose. As such, you can stick with a single [npc=112527] and keep checking back for new pamphlets (there is a 15 minute cooldown after speaking to one, which applies to all of them at the same time).

Important notes:

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• Collecting all of the pamphlets will grant the achievement, It All Makes Sense Now.
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• These pamphlets are NOT unique, so you can get multiples of the same type.
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• The 15 minute cooldown on these Doomsayers only counts down when you are logged in! Therefore, if you log out and log back in hours later, you will still be on cooldown (until 15 minutes of in-game time has elapsed).
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• You can safely vendor/delete these after receiving them - you will still retain achievement credit for having obtained them.
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• This Feat of Strength is NOT account-wide - you must get all pamphlets on a single character.
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• It appears the invisible "cooldown" debuff does not persist through death! As such you can kill yourself (fly up high and dismount) and corpse run or be resurrected by a friend in order to immediately get another pamphlet. As below, this can be repeated over and over to get the achievement very quickly!
  
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  • You can use Soulstone, Reincarnation, or [item=127770] to help with this.
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  • If you choose a Doomsayer near a Spirit Healer, you can repeat this process over and over, and run back fairly quickly. This will avoid the 15 minute wait, but will instead incur a 2 minute wait for each rez.
    
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    • The Doomsayer at [45,51] (Valley of Wisdom) in Orgrimmar is close to a Spirit Healer
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    • The Doomsayer at [47,50] (Cathedral Square) in Stormwind City is close to a Spirit Healer
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    • Be sure to put your gear in your bags before doing this, to avoid repair costs!
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  • If you take [spell=15007] at the Spirit Healer, you can skip the 2 minute rez timer, but you will have this debuff for 10 minutes. Doing it this way is the fastest route to getting all of the pamphlets you need!
    
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    • You need to put your gear in the bank if using this route and wanting to avoid repair bills, as items in your bags still take durability loss with [spell=15007].
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This achievement will be a Feat of Strength (similar to Tripping the Rifts from the Cataclysm pre-expansion event) that will not be obtainable after Legion launches. It cannot be seen until it is earned, but it can be tracked by pasting the following into chat:

/run AddTrackedAchievement(11065);

To stop tracking it, you can right-click the achievement tracker list and click "Stop Tracking"

Other achievements available exclusively during the Legion pre-launch event include:

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• Stand Against the Legion - Complete any one of the invasion scenarios during the pre-launch event
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• Defender of Azeroth: Legion Invasions - Complete all 6 of the invasions during the pre-launch event
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Azeroths greatest heroes comitting suicide because of small pieces of paper.

Doubt the Legion expected their plan to work so well.