I recently went to Upper Antelope, and used the Rokinon 12mm f2 exclusively (you do NOT want to change lenses in that DUST BOWL!!)
results i got were fantastic- the plus is that with the manual focus WIDE angle lens, I could zone focus, stop down to say f4, and know that my depth of field was going to cover. I also used auto bracketing of -1/+1 stops, so I got 3 exposures each time I pressed the shutter button. However, I *did* the "pro camera" tour, using a tripod, christ, some exposures were 10-15 seconds.
And yes, regularly shot at ISO 1000-3200 with no problem. The mirrorless camera will let you get good shots at really slow shutter speeds hand held.
ENJOY!!!!