The only road in or out of Death Valley you should avoid is Hwy 190 on the west side coming from 395. It's steep and VERY windy. Not at all suited to a big coach, especially if you're towing.
Wife and I made this mistake last year in November, driving our 36 ft. Endeavor and towing a 12 ft. trailer with two Harleys. We kept the speed at under 25 almost the whole way down the hill and still smoked the brakes on the coach and trailer.
If I remember correctly it was something like 18 miles of 11% grade and corners so tight you better hope nobody comes the other way.