the bolster buff? with that buff you get better stats, yes, but against higher level they've got better stats, better gear, wait untill they've got expertice... also they've got more skills and talent points...
Of course if you are a good player you can win in 1v1 against someone that has a character with more level, but against a character with the same class / mirror class but more levels and that plays as good as you, you are done.