Hi and welcome! This is present in my 2011 also. You will hear many suggestions of how you will use your time and money to fix subaru's poor design! There will also be others to tell you that the legacy is solid as a rock on the highway and that you cant drive or are stupid in some way, please ignore them! There truely is something wrong with your car. mine also and a few others here.
There has been some mention of people having luck with modified alignment specs and new tires. BUT ITS NOT COVERED UNDER WARRANTY. maybe you can start fighting with the dealer now and get subaru to buy it back in the near future.
I've personally been able to talk 3 people from buying the legacy just by letting them test drive mine on the highway. Its a shame you will have to deal with subaru now. best of luck. Keep us updated.