Treasures of the Forbidden Reach

The various treasures each have lots of spawn locations. With the exception of the Forbidden Hoard they are not indicated on your map in any way but they do have the signature purple outline shared by many lesser treasures this expansion. Using Anomaly Detection can help greatly with seeing them while flying around.

While there are too many coordinates for me to know them all based on limited PTR testing, I can list the coordinates I found mine and suggest you look in the general thematically relevant locations (like looking near the Farscale Naga for your Farscale Cache).

Forbidden Hoard - Spawns all over the Reach. It will show on your map when it's up. Defeat the nearby mobs to unlock it.
Avian Trove - Spawns all over the Reach, usually near the base of trees.
Obsidian Coffer - Spawns all over the Reach, but I've had a lot of success near and in the War Creche.
Spellsworn Reserves - Spawns in the War Creche near all the Elite Spellsworn mobs.
Bone Pile - Spawns all over the Reach, maybe slightly more commonly on Dragonskull Island but that could be anecdotal.
Farscale Cache - Spawns anywhere where you can find Farscale Naga, like the Siege Creche or the eastern shores of the Reach.
Irontide Stash - Spawns on the small islands and coasts where the Irontide Pirates are found.
Storm-Eater Cairn - Spawns all over the Stormsunder Crater in front of the Siege Creche.
Stonescaled Cairn - Spawns all over the Stormsunder Crater in front of the Siege Creche.
Blazing Cairn - Spawns all over the Stormsunder Crater in front of the Siege Creche.
Frozenheart Cairn - Spawns all over the Stormsunder Crater in front of the Siege Creche as well as Froststone Peak.
Morqut Provisions - Have yet to find one so it may be bugged on the PTR but the name would suggest you'd find them on or near Morqut Islet.

One of many spawn locations:

/way #2151 36.09 33.97 Forbidden Hoard
/way #2151 57.81 51.69 Avian Trove
/way #2102 53.03 52.43 Obsidian Coffer
/way #2102 51.20 58.03 Spellsworn Reserves
/way #2150 87.96 50.22 Bone Pile
/way #2151 72.05 68.00 Farscale Cache
/way #2151 35.06 47.91 Irontide Stash
/way #2151 69.36 63.79 Storm-Eater Cairn
/way #2151 73.64 56.74 Stonescaled Cairn
/way #2151 71.25 59.77 Blazing Cairn
/way #2151 60.79 25.47 Frozenheart Cairn

Edit from live: The [item=204558] purchased from [npc=200566] will mark these treasures on your minimap for 1 hour, making them significantly easier to find.

For the love of jesus, just buy The Reliquary Scroll of Perception purchased from Cataloger Daela, this will mark these treasures on your minimap for 1 hour, making them trivial to farm.

Seems like all I find are Bone Piles zzz I have found at least 2 Bone Piles in the same locations, so spawn locations are static but varied
/way 37.35, 67.74
/way 36.91, 46.54
/way 38.03, 47.31 Inside Cave
/way 56.16, 44.23 On rock by the big tree next to the waterfall

Irontide Stash
/way 35.74, 17.41

Storm-Eater Cairn
/way 71.90, 58.18

Stonescaled Cairn
/way 72.31, 57.28 up on the ledge next to the hollowed out tree trunk before the big blue swirlie pylon

Avian Trove
/way 51.30, 47.00

Morqut Provisions
/way 37.76, 82.23

Obsidian Coffer
/way 70.43, 14.15 Inside Cave at the very back near the Failed Experiment
/way 52.36, 49.05 in a small bush (giggity) by the big tree

Farscale Cache
/way 79.29, 62.89

Don't forget to use your [spell=382499]. This will show the treasures from farther away and through walls.