Let the word flow through your mind. What do you feel?
Some may feel emotions of pain, of longing for the unobtainable, of "Blizzard pls!" Others, of disgust and revulsion. And still others may think, "what the heck is a sandreaver?"
Well, what am I here for if not to explain? The sandreavers are those strange centipede-like Silithids way back when from the Ahn'Qiraj raids.

Yeah. Those ones!
Anyway, some of us here on the forums have been clamoring for them to be hunter pets for ages. Regardless, they went mostly ignored after their addition until Cataclysm, where one was added as the boss for a Tanaris quest chain. At this point there's a whopping total of three Sandreaver NPCs.
Nothing new happens in the sandreaver department until Draenor. One or two NPCs using the sandreaver model were added, and quickly noticed in the WoD beast thread. But these aren't considered sandreavers by name, only "drift lurkers", "vent scuttlers", and "scavenging crawlers". So you might think Blizzard just wants to utilize an underused model for the sake of variety.
But wait - what's this, over on the Sunset Shore in Talador?

An entire hidden colony of sandreavers, just scurrying about the shoreline?


There's no quests, no Draenor treasure, no rare NPCs to be found here. There's no purpose to the entire area. So what are all these sandreavers doing out in the middle of nowhere?
Now, I have no answer for that question. But after a little bit of searching, I also found the following sandreavers:
Sand Reaver
Gorgrond Sandreaver
Giant Gorgrond Sandreaver (A rare!)
Wow! So it looks like our sandreaver friends were going to have a bigger presence in this expansion. They were all added with patch 6.0, but remain unused. I wonder what else never made it into Gorgrond...
Gorgrond Sand Worm

A sandworm, huh? And the Silithid model, too. Hey, wait, aren't the sandreavers Silithid? What are they doing in Draenor?
This is strange, let's do some searching to see if there are any more sandreavers out there...
Kuraki Sandreaver

Wuh-oh. That's not a regular beast, that's a Nerubian—those undead arachnids we last vanquished in Northrend! This is something big... bigger than any of us could have imagined--
Wasteland Scorpar
Scorpar Sandsinger
Scorpar Dunestalker
Aridmancer Ti'chent
Aridmancer Clan'dok
Aridmancer Xon'cah
Dur'ukal
Skel'ukal the Baleful

Kurak'akan <High Dune Shaman>

Wow. Looks like a full-fledged army of Nerubians and "Scorpar". Judging by the names of "Aridmancer" and "Dune Shaman", I'm inferring those particular NPCs wielded sand-shaping powers to desertify the landscape. By my guess, they'd probably be going after the jungles of Gorgrond to make it more suitable for their purposes.
And sure enough, here are some fragments of a vignette event:
Launch Vignette: Scorpar Ritual
Launch Task: Scorpar Husks
Scorpar Husk Fragment
Credit: Scorpar Cave
Credit: Scorpar Leader
Kurak'akan is Dead
It looks like we were to disrupt a Scorpar ritual (an desert-making ritual?), kill their High Dune Shaman, and collect the husks of their bodies.
Now, obviously a lot of this is speculation. There's been cut content in every expansion, with Warlords of Draenor being one of the biggest offenders. Game Designer Don Adams said this of the Scorpar:
"Creatures we ended up cutting. You won't see them in WoD. At least not at launch..."
"To clarify, maybe never."
But even if these NPCs and events never show up in game, it's still interesting to think - what were they planning? Personally, between all the isolated or otherwise unused silithid models, the Nerubians, and the Scorpar, which are clearly meant to be the Draenor version of the "Old-God created bug race", I think their forces were going to be a relatively significant secondary/tertiary antagonist throughout the expansion. I, as a big fan of these kind of enemies (and the potential tamability of their more bestial allies), am still hoping for these creepy crawlies to show up in a post-6.2 content patch or even reused for another expansion.
So for all these great questions: is there an Old God presence on Draenor? Are there hidden cave networks of bug-people, waiting to strike and turn all of Draenor into a desert as the major forces of Azeroth and the Iron Horde become distracted by the onset of the Legion?
Until the next expansion or two, we can never be sure.
And it all started with the sandreavers.