Depending upon the geography and the species there is no average. Within the bush habitat we hunt in the north the ranges for most species will be from 50-150 yards.
In Namibia a shot of 300 yards on Gemsbok, zebra, eland, springbok, etc. would not be exceptional. As far as game toughness........highly debated and tons of opinions. I was born and rasied in the USA having hunted most of the big game. Also worked as a guide in AK for a loooong time. I've hunted most of my adult life in Africa. So here are my thoughts on this having experienced many of the speces tenacity of life in fairly large numbers.
Everything shot through the heart will die, just as it will when shot through the lungs. The difference is the distance/or time it will travel before it dies, and the amount of blood given to locate it.
Some things to consider incude anatomy, which is the biggest issue for my hunters and one which I cover in great detail with all the hunters in camp before each hunt. The depth of the chest from brisket to backbone is a greater span in many African species. Many Americans who aim for the middle as they would at home shoot far to high for the organs and far to low for the spine. There is always a story later about how tough the animal was. "It was hit perfectly through the chest and ran miles without ony blood".
African game for most of the larger plains species has much thicker skin then American game. Kudu being an exception. Zebra, wildebeast, gemsbok, Hartebeest, Tssessebe, sable, etc. even the warthog have extremely thick tough elastic skin comparable to NA Mtn Goats, and wild boar. This is a much tougher to penetrate and bleed from substance then other game around the world. The thorns and hooks these animals live in have likely been the evolution of this very tough hide. The toughest hides are typical of herd animals which spook and run wildly through the bush to escape in a panic. Animals like the Kudu which are not herd animals but rather live in small family groups use stealth and skill to evade rather then blinding speed and brush crashing.
Speaking of herd animals. Another issue with plains species is the typical dry dusty conditions and the sandy soil. Combined with being herd species make for extremely difficult tracking at times. In North America almost all game shot will be a lone animals. Once shot you can watch the reaction and departure of that animal for some period of time.
Now switch to Africa plains species like a Zebra, Gemsbok or Wildebeest. You see a trophy you wish to shoot and it's among 25 other animals. When the shot is clear you take it. At that instant all hell breaks loose in a plume of dust so great you can hardly see through it. Much like a shell game, the animal you shot becomes lost in the stampeed. Not only that but using a small caliber rifle reduces the blood flow. The only spots of blood are now covered in the settling dust and what do you have? ........nothing. Yet you are sure of the shot placement.
Herd mentality will push game many levels beyond anything you can imagine to stay with the group. Now 1/2 mile or more without any blood trail and the game is lost. African game can seem much tougher when this happens. The same event with a single bull elk, deer, bison, moose, etc would be much easier to follow up visually letting you see what happened. Then tracking a single animal is far less complicated then trying to follow a thousand foot prints in the sand to find the set from one you shot.
As you follow this group trying to keep up, the sick one peels away from the group and slowing down it will lay up and die. Yet you pass that single set of tracks up while folloeing the group. Finding one set of tracks that peels away in a 50 yard wide stampeed made by 25 or more animals is a needle in a haystack. When you see the group again you cannot identify any that are sick, and none with blood. Only then you realize it's somewhere behind you. Good luck!
Yeah African game seems tougher and the conditions can be difficult with the herds, and anatomy, and the much thicker skin. As I said anything shot in the heart or lungs will die. The real question is how long will it live after that and how far it can go. It's my opinion having hunted professionally in both Africa, and North America( including AK) that more game by a large margin with what seems like good shots and good equipment is lost in Africa then everyplace else I've worked combined. I'll add to that more game is shot there too. Which also has to be considered.
There is great difficulty folloing bears in SE AK when its a drizzle in the wet rain forest areas and the hunter has used a small caliber rifle. That is just as difficult. But we are only talking one species. Africa has so many speices that can cause this stress, it creates this feeling they are tougher.
They are tougher to find, I have spent far more time looking for African animals then NA animals. That ratio is not even close! I'm not talking about the shot placement or bullet quality. Just a good hunter making a good shot and having the animal run and die in a situation that took a heck of a long time to resolve.
I think the thick skin evolution because of the thorns, and the herd life style do make them more difficult to locate. I also feel they are a bit tougher or more willing to run and fight for their last breath.
Elk, Mtn goats, and wild hogs are the three toughest NA game I've seen shot and keep traveling a long way. Moose could be added to that as well, but it's more their shear size that gets them a lot of bullet impacts without falling. You could say the same about Austrailian water buffalo, American Bison and Eland. I have to seperate real tough to kill animals from those that are just so big they can take a pounding before death sets in.