I'd say the .458 is one of those " fair cartridges " . Those who dislike it , dislike it with a passion. Those who like it , find it " fair " . There's a book written by one of my favorite fire arms experts , Mike LaGrange . It's called " Ballistics in Perspective " . In it , he mentions that the .458 Win Mag is uses by far , by the most professional cullers. But he goes on to say that while it gets the job done , it is far from the most ideal cartridge for the job.
When my Granddad went to Kenya in '68 for his Safari ( where he dropped a bull elephant with a shoulder shot using the .375 HH Magnum which l own now ) , he observed that all the PHs there were armed with Winchester Model 70 rifles in either .375 HH Magnum or .458 Win Mag. But he also reports that MANY people were unsatisfied with the cartridge and it's lack of penetration . This prompted many PHs to use a .375HH Magnum for all their DG hunting.
This is corroborated by the Hunter , Harry Manners who also thought very poorly of the .458 Win Mag. You can find a 4 part video on you tube of a man who went on a safari with Harry in the 1960s . In the video , he reports 5 shots from a .458 being needed to put down a Bull Elephant.
Now , on the other side of the spectrum b, you have Harry Selby , who actually sold his infamous .416 Rigby and used a .458 Model 70 towards the end of his hunting career and was very happy with it.
Me , personally ... I had the good fortune to hunt a brown bear with a. 458 Win Mag in 2010 . It was an Original BRNO ZKK602 belonging to my childhood friend , Evan ( ironically , that's the gun that got me loving the BRNO actions so much ) . The gun couldn't feed soft point ammunition reliablyely , but with a solid FMJ , it completely pole axed that huge bear. Of course , bears don't even come close to African elephant or buffalo.