adamlanghans

Have you tried setting Menu > Global Settings > Output Level as "Line" instead of "Inst"?  Alternatively, did you previously have any Global EQ settings which were reset?

There are so many factors when playing live that greatly overshadow the difference between listening via headphones and live.  The venue's acoustics, the PA speakers, the direction they are pointed, where the listener is standing, etc.  Using your headphones to build a patch will be perfectly fine for building tones.