It might take 4 hours to find yourself a mastadon, but likely one shot was the fatal one. . .in all likelihood a stab to a major artery in the leg or neck. I dunno if you've ever been hunting, but generally you don't turn the target into hamburger until after you clean and butcher it, you don't want to nibble the target to death, you want to put it down with one shot and damage/ruin as little of the meat as possible.
Native Americans would kill Buffalo with a single arrow behind the foreleg, getting a lung or heart shot. . . .similar tactics have been used with spears on rhino and elephants. . . .
In terms of Bear, usually you had to kill it in one shot, or it killed you, that being a problem with rolling up on megafauna with a sharp stick, if you're close enough to kill it, it's close enough to kill you.
There is zero record of how actual stone age era hunting practices were conducted on now extinct megafauna like Mammoths and Giant Sloths and such, other than comparative study of stone age cultures that existed up into the near modern era. . .but killing Brown/Polar bears with bows and spears, killing half ton boars with bows and spears, killing rhino and elephants with spears or lances, and killing tonne weight walruses and seals and up to mid sized whales with harpoons. . . .all generally accomplished to hunting standards. . .i.e. one shot one kill, or at worst, one shot one down then cut it's throat.
Having to hack something up with an army is what you do when Hannibal charges war elephants into your legion, but destroying the prey meat aside, any hunt that assumed some of the hunters would die wouldn't be a hunting tactic that hunter-gatherers would pursue. . .we naked apes are indeed killing machines, and no animal that ever lived could survive a clean hit from a lance charge on horseback. . .the forces involved are immense, and sufficient to penetrate the hull of a lightly armored vehicle, so perhaps even a dragon would be wary, and potentially open to a one shot kill. Even a monster the size of a building can be one shot killed if it's spine, organs or a major blood vessel run within weapon length of their surface. . .a sword can punch in a couple feet, a spear can be thrust in yards. . .ignoring the fact that likely makes a torso single kill shot possible if hard to do, how thick is the neck, or the limbs of that dragon?