No doubt that a double rifle is probably the first choice of any hunter/ph but they are not a absolute with everyone. Plenty of the most famous ivory hunters used single shots, Selous even used a muzzleloader for a larde chunk of his career, and no one can say that he wasn't successful. WDM Bell favored a bolt action in a caliber that isn't legal to use on big game anymore, .275 Rigby. It's rather pointless to argue over the necessity of a double when in fact it's not a requirement.

Shot placement is better than a rifle with four barrels any day, the only reason a double is needed as a "just in case" senario. For me, when accuracy is the most important criteria in a rifle, then a single shot or bolt gun with a good optic is what is needed. If you actually look at bolt guns by Blaser and how fast you can cycle the bolt, it's significantly bridging the gap between doubles and old style bolt guns. I recall some one, it might have been Boddington, but they raised the good point that if 3 shots are required than a bolt guns greater capacity can trump a double. At the end of the day people should concentrate on putting that first shot on target, and they won't need a second shot, and secondly to practice, practice, practice before you hunt so that it becomes a reflexive movement to put a second shot on target if needed