Echoes of Danger

Here's a command that should work to help you track your progress in each event and zone. It's short enough to be added as a macro or pasted directly into the chat window:
/run C=GetAchievementCriteriaInfo m={1,2,7,8,5,6,3,4} d={5,6,4,3,1,2,7,8} for i=1,8 do z=C(20596,(i+i%2)/2) n=C(40252,m) r=0 for j=1,5 do _,_,c=C(40222,j+d*5-5) if c then r=r+1 end end print(z..':',n,'-',r..'/5') end

Isle of Dorn

Worldsoul Memory: Ancient Explorers: (South)

Stormlord Kao'dar
Toaka the Explorer
Conqueror Or'sosh
Wavecrasher Jurvak
Warmonger Ogli

Worldsoul Memory: The World Carvers: (North)

Gong'tze the Riverhewer
First Blade Grimskarn
Zeeben and Zillix
Talinhet
Temaya

Ringing Deeps

Worldsoul Memory: Primal Predators: (South)

Kiji the Stomper
Clawmother Tengi
Nalo'xic
Pterrordaxus
Tor'go

Worldsoul Memory: Elemental Fury: (North)

Flame Viscerator Ignes
Oremex Flamebreaker
Earthfury Cragshar
Deepwalker Cavelord
Crateron

Hallowfall

Worldsoul Memory: Reign of the Old Gods: (South)

Aqu'yinra
S'toth The Insatiable
Bor'zal the Lurking
Yor'sith
Venox

Worldsoul Memory: Descendants of Distant Waters: (North)

Hand of Azshara
Zaniga the Tracker
Ankoan Champion Utaari
Gurl the Feaster
Utmoth the Tidetwister

Azj-Kahet

Worldsoul Memory: Old Gods Forsaken: (South West City of Threads)

The Rebellious Queen
Spiz'na the Traitor
Vin'ris the Corruptor
Vil'vim the Mindtwister
Yoh'nath the Ender

Worldsoul Memory: A Wounded Soul: (North East)

Shard of Gorribal
Dregbile and Soulboil
Azerite Manifestation
Widowcore
Heartsear

I've received this achievement today after completing a little over half of the required rares that have to be killed. Here's a Screenshot

My guess is that the achievement is changed to kill 20 of the 40 unique rares but the text still says that you need to kill all of them. I assume this will we changed in a future patch.