Well, I've lived in Phoenix for 30 years so I'll venture an opinion.
The minimum I'll wear is Dragin Jeans. They are kevlar lined and offer much better abrasion resistance than regular Levis. That kevlar lining gets a bit warm in the summer though. Riding with a sheepskin seat pad can help, but hot is hot.
You say you don't want overpants, but I'll just add that a mesh overpant can be worn with shorts and provide a very nice breeze for the boys. That said, when it goes over 110 that breeze can be a bit less than comfortable.
If you are willing to spend some money I'd make two suggestions. Check out Motoport as they make some excellent mesh gear that is very highly regarded. Second is the BMW line of clothing. Their stuff is top notch and priced accordingly.