THIS ISSUE HAS BEEN RESOLVED AS OF 4/20/2014 - 08:55
I figured out the issue, and I don't think it's just north stratis that has this problem but it's still kind of wacky. If an AI is driving to a waypoint that is NOT on a road, it will make a beeline to that waypoint from its last waypoint. This can be fixed by placing a waypoint on the road where you wish for the vehicle to divert off the road. However, I have been in AI vehicles where they automatically calculate this themselves, no extra waypoint required. This still may need patching but it is certainly less urgent now.