Winning the Australian Open 2011 and 2012
Winning in I.W. 2011, SF in 2012
Winning in Miami 2011 and 2012
Missing the Monaco Masters in 2011, Final lost clearly to Nadal.
Winning Madrid in 2011, failling to do the same in 2012 but on different conditions.
Winning Rome in 2011, loosing the final in Rome in 2012, not as bad as in Monaco though.
SF in Paris in 2011...final in 2012 lost to Nadal ( in 2011 he probably would've beat Nadal on Paris clay seeing what happened then in Madrid and Rome ).
Winning Wimbledon in 2011, loosing to Federer in another clear defeat similar to the ones vs. Nadal on clay.
Winning Rogers Cup in '11 and '12
Loosing the Cinci final in '11 and '12
Winning the US in '11 and losing the final in '12 but I'm pretty sure that in a way, his North American hard court season was 99% the same as 2011, the difference was made by those 2 match points saved v. Federer in the SF and that Nadal was a much easier victim on this surface anyway ( would've beat him in 2011-2017 in the US Open finals ). Really not a decisive difference between August-September '11 and '12.
In a way, Nadal was way more dangerous on clay in '12 than '11, Federer was miles ahead in '12 than he was '11 ( till the closing stages of the year, when he won Basel, Paris, London Masters ).
Clearly he could've done better in '12, but both Rafa and Roger made progress.