I believe players are slowed due to non leg injuries, so animals should be as well. However, the key to endurance hunting is to stress the animal so it runs (to build up fatigue), and do so often enough that it doesn't have time to recover in between being forced to run. At the same time, the player can't run constantly as that will slow the player down to a crawl.
The speed of the player is important, I think. A high speed player with a 7 km/h walking rate seems to be able to get elks and reindeer to run into the ground by walking (provided the tracking is sufficient), while my current 5 km/h player (about average) was thwarted by a reindeer who could recover by just walking away in more or less a straight line.
If you can corner the prey so it constantly runs back and forth along a river or lake shore it's fairly easy. If you can drive a calf away from its mother is should be reasonably easy as well, as the calf should try to return towards the mother, and if your player is in between to cause it to run again you may be able to bring it down reasonably quickly, and the same goes for reindeer in a herd, as they try to return to the herd, rather than walk away from you in a straight line.
I don't think eye sight affects your assessment of the prey's status: I think you get it all if you're able to see it (and I think eye sight only affects detection).
I'd suggest you take another look at your new character's speed stat (or just look a the walking speed), as I suspect a 3 km/h slowpoke would have trouble endurance hunting anything not hemmed in. If the character has poor speed, you may consider changing the strategy (e.g. towards traps).
Terrain matters as well, of course. Spruce infested forest is a pain due to the poor visibility, so you're often reduced to tracking rather than moving directly towards the target when it comes into what should be visual range again, giving it more time to recover before you scare it into running again.