Rough riding 14 Legacy

I bought a 2014 Legacy new in Dec 2013.  My wife wanted it but I thought then that is had a rough ride but I didn't realize how bad until I got on a washboard road.  Large bumps like railroad tracks don't seem to bother it and it takes them in stride, but on a washboard or older road surface that has a lot of small bumps and this car sounds like it is shaking apart.  It makes more noise than an old logging truck.  It sounds like a jackhammer hitting the bottom of the car at all 4 wheels.

At first I blamed the 50 series tires (215-50/17) so when one got damaged by a rock at 50k miles, I replaced all 4 with 215-55/17.  It helped a little but it is still the noisiest vehicle I have ever driven on washboard roads, and I've been driving cars, trucks and buses for 55 years, including military trucks up to 5 tons.  Anyone else have this issue with their 14 Legacy or Outbacks?