I personally have had first hand experience with this same situation, and it's one I dread after we've had washing rains (usually in the spring..we'll get as much as 4 inches of rain in 1 hour) that destroys my driveway, and has even pulled up the underpinnings of the initial construction of large rock.
I have finally come to believe the advice from so many that the driveway will always be a maintenance issue. But here's a few suggestions:
1. Have you tried buying new rock, like SB2, to spread on the driveway? This is good for stopping the muddiness. If the ground is still mushy and ruts are still forming, you may have to apply several coats of gravel...at least in the worst spots, but you still need a good crown on the road.
2. It's possible that you need a taller or better crown on the drive so water moves off to either side quickly and efficiently, this is something that the road grader can't really do.
3. In my case, I put in larger culverts this year to handle the water better so it wouldn't jump up on the road when the culverts were full (and they do get full over the years).
4. Call an experienced dirt work guy, one who understands driveways and drainage, and who has the equipment.
I lived for a number of years of just having the driveway "smoothed" back up after the washing rains, but this year I hired a dirt work guy, experienced with fixing driveways who had all his own equipment, dozer, dump truck, back hoe, etc, and after explaining in great detail what happened during washing rains and what I thought needed to be done, with his experience of solving water issues on driveways, he did a great job, It took several days and $2000, but it was in need of the improvements. Now it's great! Will it stay this way? Probably not over time, but because of the larger culverts, a nice crown, cleaned out drainage areas, and additional gravel, it will hold a good while.
Does this help?