I have only wheeled 1st gen stuff so I can't say about newer stuff first hand. I have seen folks in that area with tire trouble. You really need LT(light truck) tires. P or passanger car tires are too soft for the rocks up there. If you are running small tires and ground affects it will take a lot more work to get over everything without damage. And again it depends on driving style. For those trails gears help out a lot. I'd rather have 30's or 31's with 3.73 gears up there than 33's with 3.27 gears.
The Heep rental and tourist stuff is very important up there. They try to plow open some of the trails for Memorial Day. I plan to be out there Memorial weekend and camp up in the mountians. Gonna be cold I think. I'm gonna try to do Engineer, Cinnamon, and Ophir. Used to be Black Bear was not plowed open and didn't open on it's own till late. The rental places used to not let folks do Black Bear with the stock heepies. Don't know if that is still the case or not. So that is the reason for late summer trips. Everything is more likely to be open then.