RE: 400 Yard shots at elk? Heck with that check out this video that has a 750 yard shot at a elk!
I see your point but this one was close to home. I have perched on top of those canyons many many times and scoped out game. When its time to shoot though I can't help but look at the cover and terrain and know that if a crippling shot is made, there is no chance that you are going to work your way over to that spot before a wounded animal is in that cover. Unseen wind currents and updrafts at that range make those shots iffy as hell. If they miss then all is well but I would pass on that shot every time. Shorten that by 100-150 yards then your chances improve big time. I have shot targets at those ranges and many time the sight picture was perfect when the gun went off but no cigar. It may be true that they couldn't get any closer but thats why its called hunting. Sometimes the animal wins. Like you said though those choices will be made on the spot by the man with the gun.