I'll run with the OP, but with a wrinkle. I'm adding Safin to Fed's 2008 Wimbledon and Fognini to Djoker's 2014 AO. That gives us two players for each year.
Fed's HTH in slams vs Djoker's AO opponents
Tsonga 4-2
Murray 5-1
Wawrinka 6-1
Nadal 3-9
Fognini 1-0
Djoker's HTH in slams vs Fed's opponents above
Nadal 6-9
Roddick 1-1
Ancic 1-1
Ferrero 1-0
Hewitt 4-1
Safin 0-2
Federer, even in his older years, did great against Djoker's AO opponents. The exception here is Nadal. And Djoker faced Nadal only once whereas Fed faced Nadal 3 times during his run.
I would still give Fed a slight edge in difficulty. Roddick on grass during his peak was a bear to play. And Safin was always dangerous. I don't think that any of Djoker's opponents would have won against 2003-2009 Fed, except for Nadal.
Federer unfairly gets shredded for weak competition, even by Sampras' fans. I find it really tough to believe that Fed had weak competitors, especially since Federer has played through Nadal's and Djoker's entire peak. Fed played 80+ matches against these two legends. I also find it funny that Federer gets slammed for his poor record at age 29-31 vs the Big 3
Let's look at Sampras vs Federer, age 29-31 seasons.
Sampras 2000-2002:
2-4 vs Safin
1-2 vs Roddick
2-5 vs Hewitt
Total 5-11
age 29-31 seasons for Fed(2010-2012):
7-8 vs Djokovic
5-4 vs Murray
3-5 vs Nadal
Total 15-17
At the end of the day, hypothesizing about the level of competition doesn't really factor into my rankings anyway. If Nadal, Federer, Stan, Murray, Raonic, Cilic, Khach, Tsitsi, Zverev, and Thiem all retired today, then I would still give Djokovic 100% credit for breaking Fed's slam record.
This weak era stuff to me is a bunch of nonsense. And besides, the game has changed a ton. Can we prove beyond a reasonable doubt that Djokovic and Nadal would shred Peak Roddick and Peak Safin on the faster hard courts courts? Can we prove that 2003-2007 Fed would shred Nishi, Raonic, Cilic, Zverev, and Thiem? None of this can be proven without a time machine.
Federer earned the slam title record. If he is eclipsed by Nadal, Djokovic, or some John Doe in the future, then that player will have earned it 100%