Would the field stand a better chance against Tiger if the courses were harder?
It seems counter-intuitive; he's by far the best player out there, and it seems logical that the harder the course, the truly top-tier players will stand out.
But that hasn't necessarily been the case with Tiger. In a lot of recent majors with relatively low scoring, Tiger's won -- all three of his PGAs (even Medinah '99 had arguably low scoring; 20 players under par and -11 winning); all three of his Open Championships; the '01 Masters and arguably the '02 Masters as well.
There are exceptions, of course -- his other-worldly performance at Pebble, and Bethpage as well.
But in several recent majors with tough scoring conditions -- two US Opens at Pinehurst, US Opens at Southern Hills, Shinnecock and Winged Foot; British Opens at Muirfield, St. George's, Carnoustie and Birkdale; PGAs at Oak Hill and Baltusrol; Augusta '03 -- Tiger's either been close but not there, or played indifferently.
Would making these major courses tougher make it easier for his opponents?
I'm not sure the toughness or conditions have much to do with it. Other reasons better explain nearly all of your examples.
Pinehurst: in 1999, he was still working out his swing changes. Last year he had about the worst putting of his career there -- averaged 32 putts per round. But still he came in second.
At Shinnecock in 2004, he was retooling his swing. At WFW this year he was playing for the 1st time in months, in the wake of his father's death. At Southern Hills, he had been playing great. But that would have made his fifth major in a row. Is that course toughness, or the law of averages which he already had broken beyond belief finally catching up with him?
Carnoustie in 1999: near the end of his swing changes, but not quite there. Still almost won, on a course setup that was a crap shoot. St. George's & Birkdale: swing change period. Same with ANGC 2003. Muirfield: when he started to look at swing changes.
Baltusrol: he almost won despite an opening 75. That was after winning two earlier majors that year. Again, no one wins all the time. Oak Hill: swing changes.
If ANGC in 2003 counts as a tough course, wasn't it a tough course when he won there? Remember that in 1997, no one else broke 282 there. In 2005, other than DiMarco no one broke 283.
I doubt any course can be Tiger-proofed. He will find ways to win everywhere. Just as he has all his career.