I believe that the solid rear axle platform will always dominate the rough, big whoops terrain as it allows for more wheel travel and is a simpler design. The limitation for independent suspension is the limited angle of CV joints, although with the portal hubs that are being designed and used, I'm sure that will change rapidly in the next few years with development and use.
I would have to say the rear/mid engine truck layout with forward facing transmission and a solid rear axle that allows the rear trailing arm pivots to be placed as far forward on the chassis as possible, allowing more rear wheel travel will be the dominant design, especially in a 4WD truck.
I would say there are multiple reasons why trucks typically dominate over Class 1 cars: More wheel travel, more stable at high speeds in rough terrain, more power, and a typically higher class of driver.
Class 1 cars are now starting to use big power engines, but are still limited by wheel travel, and with the exception of a few drivers, typically don't have the deeper pool of naturally talented drivers that are in the TT class.
I would also add that if you put the top 5 TT drivers in a class 1 car, you would get a better chance of having a Class 1 overall depending on course/terrain, example CJ Hutchins doing very well at Silver State 300 the past few years, and Justin Lofton when he ran Class 1.