Consider a hot desert with temperatures between 30-40 degrees Celsius year round and 100 mm of precipitation annually. Suppose some corpses are placed on racks and predators are kept away. Sand is removed if it accumulates on the corpses. What would the corpses look like 30 years later? I imagine that they would not mummify, as there is some rainfall on occasion. Would they be reduced to skeletons? What would the bones look like?
After 30 years nothing would remain. The bones would be completely worn away. This article has an in-depth analysis:
J Forensic Sci 1989 May;34(3):607-16.
Decay Rates of Human Remains in an Arid Environment
It indicates that an exposed corpse would be mostly worn down to bone fragments with in 3 years:
As the figure indicates, after 3 years complete skeletal decomposition has already begun. After 30 years there would be nothing left.
Flies will eat them. Fast.
Flies eat meat fast. In a desert like you describe with a little rainfall there will be flies. They will show up within the day. They like it hot. It is nice and wet in a carcass. They will eat these carcasses in no time. Beetles show up eventually and take care of skin and hair.
If you are digging it, the linked wikipedia article shows the sequence and lets you know exactly what insects show up. The article does not say when because that depends. There is a pig carcass shown at each stage of decomposition and if you click the picture it states when the image was made, which is pretty cool. This pig is in the "advanced decay" stage. It has been dead 11 days.
The 5th stage image is from 1 month later and it is just bones.
At 10 years I bet not even that. The sun will be hard on these bones and they will crumble.
But you can get ancient mummies in a desert. Check out this guy. He is 3000 years old and he looks good.
As I understand it he was underground, out of the weather. There is no rain in this desert and no flies. I think the Atacma desert mummies are formed similarly.
After 30 years in a desert all that would remain would be bleached bones. Biological and chemical decomposition would destroy most of the flesh within a few years and would be accelerated by rain which would provide moisture for bacteria to work on. Physical decomposition by way of freeze thaw would also serve to break up the remains.