its not important do you nano or what lvl are you or are you augumenting on normal or nightmare.....

only diference is in what augument you do :

let me give you a example : if you have a sword and you put a comon stat and you get some skill it will be +1

if you put a rare stat it will be +2

if you put a legendary stat it will be alwais +3 (max)

let say for crit :

if you put comon stat you will get + 1-2 % crit chance on weapon rare stat is 3-4 and legendary stat is 5 - 6 to crit chance......

thet is the only diference in augumenting doesent matter is ur item nanoed or what lvl is ur char thet is just bullsh........

if your smart first you will augument item then if you like it and wanna keep it you nano it.

i dunno, I did a fair amount of legendary augments on low level gear with my low level guardian and I got shit augments. i didn't get anything like crits or AA or 10+ of any stat or +3 of a skill.