I tend to agree with the statements about it being hot, VERY hot this time of year. If you try to drive from Rafter J you will spend a lot of time in transit. It does not take long to see the Badlands loop. We have stayed a few times at Arrow CG in Wall. Fifty amp FHU. That would be my choice and just do day trips into the BL. While the area itself is huge, the loop road will allow you to see the typical sites.
If you really want to get into that sort of sight seeing, you can leave Hermosa heading west and into the Pine Ridge Reservation area and see more of the same but not as dramatic as the loop. Populated areas of Pine Ridge are very depressing however