I'm fairly sure that EXP hacking just 1 EXP will get you banned. DE probably has access to the exact amount of XP you get from 1 KILL, meaning, they could multiply your kills by [xp per kill] to get a total. If it doesn't add up exactly, then they might know that you hacked :\
THIS IS A THEORY
Now Exp hack not working
wait to next up date
thank for all ^^
Probably with that theory is you also get exp from teammates, even enemies you do not assist to kill. And there is no record of that in your profile, at least that we can see