Totally normal for that feeling in the sand if you have tractiopn control on or off. The truck will use evry bit of power it has to move through sand. Alot of the times, it's actually just a case of spinning tires......so make sure you air down to get the right amount of traction. Airing down will also allow you to "float" more across the surface of the sand, rather than having to get down in it and push through it. I've had mine out to Glamis and can honestly say that was the best time I've had in my Raptor yet. I was able to hit 90+mph at the flat drags, so I know the truck is more than capable of getting you around in a hurry. I did make sure that the TC was all the way off (like stated, hold down the TC button for a good 10 sec. until the icon FLASHES in the display, it will need to be reset when going in or out of 4wd though), had it in off road mode and general running around air pressure was 18psi. When I climbed Oldsmobile Hill, I had to air down to about 10psi. So play with air pressure (on board air compressor helps) and you'll get the hang of it.
Oh and if you're talking about being off road in dirt and then hitting the occasional sand drift or something, don't worry about air pressure and just keep your momentum up.