First off, flex is overrated. I worked hard for awhile increasing my flex, back in the days when people cared I ramped as high as 1175. Now, I keep gradually dialing it back. You need enough flex for good trail performance, but after you have enough, trail performance can actually decrease as excessive flex is increased. Excessive flex decreases stability, and enough stability is needed for good trail performance. An XJ can easily be set up to have enough flex
without using Revolvers.
Most decently set up rigs can crawl through boulder fields and huge ruts, and many times it's the line that is taken and not the ability of the rig. Where the difference in rig capability seems to show these days is in the climbs. Rovolver shackles are
TERRIBLE on climbs. They do weird things to the rear springs as power is applied on a steep climb.
I'm sure if you waited long enough for plenty of people to respond to a question, you'd find at least as many people who have removed their Revolver shackles as you would find people still running them.
And they are not WCGIC approved.