The data confirms that he's worse than Fedal, but not by as much as people might think (data from
tennisabstract):
winners (and induced forced errors) per smash (W/SM), errors per smash (E/SM), and points won per smash (PTS/SM)
Code:
PLAYER W/SM E/SM PTS/SM
Jo-Wilfried Tsonga 78% 6% 90%
Tomas Berdych 76% 6% 88%
Pete Sampras 75% 7% 86%
Roger Federer 73% 7% 86%
Rafael Nadal 69% 7% 84%
Milos Raonic 73% 9% 82%
Andy Murray 67% 6% 82%
Kei Nishikori 68% 11% 81%
David Ferrer 71% 9% 81%
Andre Agassi 67% 8% 80%
Novak Djokovic 66% 9% 80%
Stefan Edberg 62% 12% 78%
Stan Wawrinka 65% 10% 77%
Ivan Lendl 57% 13% 71%
Right off the bat you can see there are
contemporary players who miss smashes more often than Djokovic does in Wawrinka and Nishikori, and Raonic and Ferrer miss just as often. But they don't get nearly as much flak as Novak does. Fedal only miss
2% less often.
Despite Djokovic's relatively high error rate, he's still winning
80% of the points where he hits a smash... And there are geniuses on this thread like
@tonylg who suggest feeding the guy endless overheads to beat him... Yeah, if by "winning" you mean losing 0 and 0 every single time.