-first of all you need to have the checkbox for Echoes of Aldramar content enabled in the top.
-set Stone Warriors as available enemy type (should be by default when DLC is enabled)
-make sure that enemy randomness is set to "even distribution" in order to exactly spawn the units from the pool of available enemy types
-make sure your map has desert by setting the monumnt to "activated 2 stages" or 3 stages

If that still doesnt work feel free to drop the MapID so we can take better look at your settings (or a potential bug)

Map ID: WJRGLMEKMGRG49ZHZYKZ8RQ1DLKF13Z1

Pasted the ID and also dont get the warriors as enemies.
You have to change "enemy distribution" to "even" (instead of "some randomness") to make sure that they spawn.
And to make sure it will be a desert map, also set the "monument" to "activ, 2 stages" (instead of "random, 2 stages")

But also I got 4 Enemies selected with that ID so im not 100% sure its the same as orignially described in the posts description.