Nasus never had a problem with dueling other champions.
This is why the change to his Ultimate are completely unwarranted. It just spikes his dueling potential even higher on the "DO NOT 1V1 THIS GUY" chart, and fails to address his weaknesses in team fights and his boring, non-interactive early game.
The Spirit Fire changes are great. It didn't make much sense why Renekton was able to shred more armor than Nasus was, and they actually make him significantly more useful in team fights, while still retaining counterplay.
It just boggles my mind how they can do a complete hit and miss in the same patch to the same champion. Riot has been talking a lot recently about making small changes and saving larger ones in case the initial ones don't work. Where is that philosophy in these changes? I guarantee people will be begging for Nasus nerfs by the end of this patch.