I think the incredible level he's played over the years brought the best out of many on the tour. But again, based on GS results (sf/f/f), this is not as terrible as it seems, imo. Plus, the illness thing cannot be put aside.
He lost to the winners of the last 3 majors. Nadal's form has been incredible, but I am pretty sure he cannot sustain such a level year round and these lurking knee injuries will also start to affect him. I love the guy, but his physique will bring him down. As for the other guy, he is yet to be truly tested, and people will figure out how to handle his game.
Federer is not done winning majors, that is for sure. I think I am being realistic, and not (too) optimistic.