If you are hunting really big mulies and come across a sagebrush flat either up high or out next to a row of crops it always pays to sit there for a while and glass it. You need to look for either eyes, ears or the ivory tips of antlers. I have seen deer lay in the sage all day and just stand up when it is time to feed at dusk.
I'll be hunting flat grassland this year where I glassed up some Mulies while out Antelope hunting year before last. Personally, they were the largest deer as far as antler spread goes I've ever seen with my own eyes, so I hope they are still around, LOL. I pretty much plan on hunting them the same way as Antelope, a lot of glassing and using the terrain as much as I can for an approach. Using low areas, crawling, whatever it takes, ha ha. The unit does have some hilly/mountain like areas some miles off I've hunted before with nice deer, so if having trouble in the flats will try that as well.
I've hunted the desert here a lot, which can be pretty flat as well, but at least there is often chest high brush cover, washes, cactus, mesquite trees, etc., and pretty thick at times for good stalking.
Hunting is not usually a pursuit where instant gratification abounds. It takes a lot of time, practice, resources and patience to be a successful hunter. So when someone decides that an area they hunted only once without taking an animal is worthless and devoid of game, I don't quite understand it. These people usually jump from game management unit to game management unit; trying a new one every year.
Now don't get me wrong, there are people that just enjoy scouting and hunting...