I have a 30.5 Breakaway with air suspension and ross power steering. it had a tendency to wander, it now has double shocks all around and added 3 degree of caster to the front, stayed home last winter so cannot be sure what the verdict is but on short run it seemed much more stable.

Wandering and groove-following are often tire-related, in any size coach. I think metric radials instead of the old fashioned truck tires would be a big improvement.
When Complete Truck Repair in Jackson found my steering gear to frame attachment loose, they significantly reduced wandering for me. Our air suspension and sway bars provide pretty good ride and handling.