Djokovic was roughly the same at the USO from 2007-2010 + years like 2013. In 2011/2015 he separated himself with grit and a higher gear (more so in 2011 than 2015).
But yeah 2007 Djokovic was no joke, his biggest flaw was clustering a bunch of UE's together at the end of the first set to lose it.
Hahaha peak 26 years old Djokovic of 2013 was not the same, yeah sure. 2013 would have been one of Djokovic's best years if not for Nadal. In effect, Djokovic would have won 3 Grand Slams plus the ATP finals in 2013, but Nadal stopped him both at Roland Garros and the US Open.
So according to your simplistic logic, if a player wins 3 Grand Slams in a year he is at his peak, if he wins 1 Grand Slam in a year he is non-peak. According to that logic Nadal was non-peak in 2011. But you will follow a double standard of course.
Oh yes, let's rest merit to every single Nadal's victory over Djokovic at the US Open.
Nadal defeats Djokovic in 2 US Open matches = oh no, Djokovic was not at his best.
Djokovic defeats Nadal in 1 US Open match = oh yes, Nadal was at his best.
What a double standard.
In 2010, Djokovic defeated 29 years old prime and healthy Federer so he was obviously playing greater than in 2007.
To say that 2013 Djokovic was not at his peak is like saying that 2011 Nadal was not at his peak. Just an excuse.
Just like Nadal would have won 3 Grand Slams in 2011 if not for Djokovic, Djokovic would have won 3 Grand Slams in 2013 if not for Nadal.