I have mixed feelings on this discussion.
I like hearing the songs from the new album. Although, I do agree that 6 songs per night might be a tad much, especially since they're playing the same 6 songs each night. They could at least rotate out The End of the Line, Broken Beat & Scarred or Cyanide for other songs from the album like The Judas Kiss or Suicide & Redemption so they aren't playing the same 6 songs each night. I also agree that 4 songs from their self-titled album might be a bit much. I like hearing The Unforgiven as much as anyone, but if they want to add that to the set maybe they should consider dropping Sad But True. (I wouldn't mind seeing Nothing Else Matters or Enter Sandman dropped either, but let's be realistic, that's never going to happen.)
Then again, let's assume that they did cut down the combined number of songs from Death Magnetic and Metallica from 10 to 6. What's left to fill the void? Well, there's the material from Load and Re-Load, which I doubt anyone wants to hear, save the few hits like Fuel or The Memory Remains. And there's the old stuff. Don't get me wrong, I'd love to hear the old stuff. Whether it's the classics For Whom the Bell Tolls or Fade to Black, or the rarer old songs like Orion or And Justice for All, I'd love to hear it all. But to be fair, they did play a ton of the old stuff on their last tour. And I know if they did that again on this tour, there would be people complaining about the lack of new songs, or the lack of variety.
I guess what it comes down to is that there's no setlist that will please everyone.