Poor Communication

Worth noting that you can spam click the missive and get 2 credits for 1.

These items have the same predefined locations to spawn. The respawn timer is about 10 minutes (maybe even less a bit).
Here are TomTom coords for the spots I found easy to farm:


/way Talador 37.88 43.90 SM - on the wall
/way Talador 37.08 42.92 SM - near stairs
/way Talador 37.48 41.04 SM - on the sign
/way Talador 35.79 40.46 SM - wall near stairs
/way Talador 34.34 39.90 SM - pinned to the tree
/way Talador 33.78 40.69 SM - in a house, on the wall (right side when you enter)
/way Talador 33.78 40.69 SM - same house, on the diagonal wall to the above
/way Talador 33.62 39.75 SM - in a house, on the bookshelf to the right
/way Talador 41.31 42.12 SM - inside the building
/way Talador 41.98 46.31 SM - on the table


These spots were enough to just go back and get them from the start. Very easy when there's some group farming this area (most mobs will be dead). Maybe will help someone.

P.S.: SM stands for Sargerei Missives.

upd: added two more spots (from Kuraudio and Saffron)

You cannot do this achievement on the Assault on Shattrath Harbor as most if not all missives spawn outside of the Market and Harbor districts. The quest area for Assault on Shattrath Harbor will only cover these two areas making the missives impossible to destroy. I have searched these two areas several times and haven't found any missives.

You require the Assault on the Heart of Shattrath daily group quest to complete this achievement.