A few insomnia-laden thoughts.
Homogenization? It's been a factor (and perhaps, a positive for all three), though I think it's been greatly overplayed as a factor. There are many players today who look at home on HC, but not on grass or clay. The true greats will find a way to achieve.
32 instead of 16 seeded players at majors: I think that's the fairer way to do it. I'd even like less randomization. Let's say that Novak is #1 and draws #17 in the first round. Is that fair to either of them? And it's not as if Roger or Rafa or Novak came on the tour as seeds - they had to earn them.
Yep, it's highly unusual that Roger, Rafa and Novak would each smash Pete's slam count, and more or less contemporaneously. This is much more subjective, but what are the odds of John, Paul and George (not dissing Ringo) all growing up near each other in Liverpool? As to tennis' Big 3, yes reasons are mentioned to "excuse" their longevity of dominance, but why overlook the obvious: They are that freakin' great, and competitive and motivated! Perhaps, Borg was similarly great, but he burned out (and didn't play the Aussie more than once, had tough luck at USO, etc) and retired early. Pete was damn good, but not (overall) as versatile or consistent.