I've shot the 500 gr Hornady's quite a bit and still love H4895 for them. Using Win brass and CCI 250 primers. The Hodgdon loading for that bullet went up to 74 grs. That ran slightly over 2000 fps. I have settled on 72 gr as tops. That will still do mid to high 1900's.
It is hard to find a bad powder for the 458 Win Mag. Another powder I have used quite a bit is AA2460. I had 2 different lots and chronoed back to back with the same brass, bullets and primers the average was 90 fps different. So watch yourt lots with Accurate Arms powders in that cartridge.
The reason I used the 550 gr is that is the only heavy bullet I have that takes a gas check and Randy Garretts 540 gr load in the 45/70 runs 15-1550 from a 22 inch barreled Marlin and I wanted to exceed it in 14 inches. I did so.
Also a 350 gr bullet is more than enough but I like bullets that befits the caliber. I don't like 180' or 200's in a 44 or 45 Colt except for personal defense.. The sectional density of a 350 gr 458 bullet is the same as a 160 30 caliber bullet and I wouldn't use that weight in a 30 caliber. 180's is what I would use.
Of course I am off center myself so one cannot pay much attention to me.
A 400 gr to me is just beginning to enter the picture for me.
BTW a guy I know shot a whitetail with a 350 gr Hornady, I believe, or it could have been a Speer, I forget now and said it put a football sized hole in it. I never saw the deer so can't speak as to the veracity of his statement. He was using a 13 inch 458 Encore I do know that.