Good points, all.
Both par threes ranking in the eight hardest holes doesn't really say much in my view. The "eighth-hardest hole" is, after all, average in a group of eighteen. Besides, there just didn't seem to be the possibility that any particularly low or high score would be made on either of the holes; players seemed to arrive at the tee, hit a shot on or next to the green, proceed with par or so.
By "role," though, I mean more than score relative to par. I'm including intangibles like those presented by 12 at Augusta. 17 and 18 at TOC present this; on those holes, anything can happen when things are on the line.
As to the suggestion that 9 and 18 be changed to Par 3s, I disagree. They're par fours. They may be obsolete now, but they're par fours.
WW