IMO, that rust is not that bad for a 4 year old car. We use salt on the roads here like crazy. Welds rust first on every single car I've ever worked on. However, I have never seen it become an actual structural issue. The sheet metal rusts through before the weld is eaten away since it is thicker. Is it ugly? Yeah. Is it an actual problem? I don't think so.
__________________________________________
View my fuel log 2015 Mirage DE 1.2 manual: 47.2 mpg (US) ... 20.1 km/L ... 5.0 L/100 km ... 56.7 mpg (Imp)