Wawrinka got lucky not to play Roger in 2 of his winning slams and in the other was a clearly disadvantaged Federer who had to play 3 straight days.
Same for Murray who doesn't ever played Federer at all at his 3 Slam wins.
This part of your post is silly.
2014 Australian Open- Wawrinka beat Djokovic who is the obvious guy to beat and toughest foe here, not Federer. Regardless if you think Federer would have beaten Wawrinka or not (I think Stan would have won) he wasnt lucky to not play him when Federer at that stage of his career was super unlikely to make an Australian Open final anyway (last one was 2010) with people like Djokovic and Nadal almost certain to beat Federer if they played, and many others like Murray, Wawrinka, Tsonga, with a good chance. Keep in mind Federer was the 7th seed so avoiding both Nadal and Djokovic to reach the final would be nearly impossible, and the only way he would have even made the final would be to play neither.
2015 French Open- Yeah like an old Federer was ever going to be a threat to win Roland Garros. Wawrinka won their encounter easily, so obviously wasnt lucky, and if you think a fully fresh Federer wins their match here you are utterly delusional.
2016 U.S Open- Given the year he was having I doubt Federer was ever going to be a big factor this time around if he played the Open. He might have had a decent shot to beat Stan if they played anyway given the surface and the match up, but he wouldnt have likely even reached that far.
Murray you may have more of a point on but:
2012 U.S Open- Federer found a way to lose badly to Clown-dych of all people. Hardly a worthy champion. Murray also successfully beat Djokovic who was clearly the guy to beat on hard courts by now, not Federer.
2013 Wimbledon- Federer was in terrible form all of 2013. I very much doubt he beats Murray here, or even reaches him.