Paul,
Pat Mucci has had a lifelong love affair with NGLA and nary a discouraging word can have any merit in his closed mind. A world-class finishing hole? It is excellent, but does not attain the status Pat confers on it. It is a short par 5 where driver isn't called for. There is a very conservative way to play the hole which takes all the hazards out of play and makes 4 a slight possibility but makes a 5 highly likely with no worse than 6 possible. Going for it in 2, well that brings other scores into play as with Merion at the same length but with hazards that are more in play, more topographic movement and a far more demanding green complex.
Pat mentions that Merion has been stretched over time. So was NGLA, just not nearly as recently. Too bad Macdonald didn't foresee the distance impact and buy more land or route with more elasticity in mind. Elasticity would help greatly as at other of his courses. But there isn't any on the final hole. I'd play it as a par 4 so no lengthening is required and the psychological impact would be an improvement.
By the way, speaking of safety net, what do you think the bunkers behind the 18th green at NGLA are for? Increased intensity or an aid to going long? That green is so wide open in the front that there is not much of a "fear factor" going on at that end. Merion and Carnoustie have a much more scary green surround than NGLA.