If you dont have cc or a tank hes going to run over your team. If you got anyone who can stand in front of him and slow him, he just falls over. I play ADC, and I main ashe, but I never care about seeing Nasus. Most of the time they end up having to teamfight, get stuck on the frontline CC'd/slow'd to death forced to hit a tank and they rarely have Arpen so they do nothing but get shredded down, trying to get to me or another squishy. The only time they really seem a problem is if everyone on the team is squishy, and/or they get to freely splitpush and never have to teamfight.
I mean looking at your team comp, how the hell did Nasus EVER get to anyone? You had, Sejuani/skarner/Veigar/Varus. He should have just been stuck. And no, your Varus did not have LDR. He didnt even have Last Whisper.
Problem is everyone in low elo plays smear the ADC, and there is no concept of peeling or ccing anyone except the person you are trying to kill, which is always the ADC.
I mean I JUST faced a Nasus and he could never get past the Cho-gath.