A couple things to throw in the mix.
One, a lot is said about how Rafa's attritional style has negatively impacted his career. On the other hand, he's almost 32 and #1 in the world, so it isn't like he's wheelchairing himself onto court. It may even be that his frequent injuries actually prolonged his career. From 2004 to the present, Rafa has missed 8 Slams - that's two year's worth. I'm not saying he's actually 30 in "tennis years," but maybe those two years worth of missed Slams have lessened the wear and tear a bit.
Re: Novak. People bag on him for mental weakness, or at least not being as strong as Fedal. I'm not sure I agree with this. Remember, this is a guy who was #3 for four years in a row, always a third wheel. But then he found a higher gear in 2011 and surpassed a still potent Roger and g Rafa at his best. No small accomplishment. His 2011 and 2015 are better years than any of Rafa's, and as good or better than Roger's best years. While Novak doesn't quite have the same career accomplishments (although he's not far behind Rafa, closer than the 4 Slam differential would suggest), he's in the same conversation of "first tier greats" and has his own unique stamp of greatness.