How can I find the ancient device with less searching?
I actually am doing it a different way and I find it much faster. Rather then using the South end checkpoint, I use the one in Zoltun Kulle's Archive to the North west. Walk directly east across the bridge and you run right into where it spawns. When it spawns the first thing you will see is a semicircle pit with bones in it, that's how you know you got the right spot. You see it about 10-20 steps away from the bridge when it spawns, if its not there I reset. I've been running it over and over again both ways (only need 2 more to get the achievement) and coming from the top is much easier to immediately spot it and leave if you don't.
There are 5 other spawns that can take place in either of these locations to my knowledge: 1.) Tar pits (Nothing) 2.) Giant Boneyard (Nothing) 3.) Giant Spiral with a Resplendent chest 4.) Giant Circle with a Resplendent chest 5.) Urns that contain Pazuzu (Though these might spawn in the lower half only, because thats where I usually find them)