I can't honestly say I ever lost to a pub within a 5 level range 1v1 in open world....ever. In my experience, it's the PuBs who are really crappy.
Well, I got to take that back now, my Jugg got owned by a Sentinel the other night on Illum. Was a close fight the first time, although he had the NPCs on his side, but second and third fight, after I burned my cool-downs, he obliterated me. Had a lot of fun, and wish I could remember his name for the life of me. I'll eventually want a rematch.