You Had it Coming

As commented by YariniCeteri, this achievement can be earned by using the Swapblaster to kill yourself.

The specific set-up I used was: have a friend stand at the edge of a platform - we used the starting platform in Algeth'ar Academy - then have them jump off the edge. While they are falling, use your Swapblaster. You'll take their place, fall to your death, and earn the achievement!

Got it on the PTR while servers were down this morning.

Need to swap someone and then die. There seem to be restrictions on it as it didn't work for us in a few places but I can confirm it works in Mythic Algeth'ar Academy.

We walked near an edge at the start of the dungeon, swapped and jumped off to our deaths. It may require a current content instance to accomplish because the same thing did not work in Orgrimmar, Valdrakken or Blackwing Descent. Can't zone in to non-legacy raids on PTR so we couldn't test out DF raids but it definitely works in DF dungeons.

Big thanks to both Trauk-Blackrock and Ryken-Stormrage for helping test out various theories!

I wonder if you can swap with a friend standing on the press in Dornogal to get both this and Flat Earthen at the same time.