I recently had an epic battle between my character and a bandit camp of ~50 enemies. I only died because I didn't pull out a crossbow bolt in time, and got an infection after the battle.
I charged the camp like an idiot, but saw about 5 ranged units, so I hid behind a tree and let the melee ones come to me. I focused on crippling attacks like broken bones over killing shots, since units in pain tend to run away. I lost my weapon hand to a crossbow bolt, but I used the glitch where you can take something out of your backpack without an empty hand to put my sword and shield in the same slot. I threw the rocks that I'd picked up before the battle, and managed to cripple 5 or so enemies with just that.
So, lessons I learned from that: breaking an enemy's bone is as good as killing him if you're facing a large horde. If your enemy is in pain and you move away, he'll run away instead of chasing you. They'll come back later, but they'll come one at a time, so they'll be easy enough to kill later. Stay away from ranged enemies, a single crossbow bolt can mess up your whole day. You can attack the head for a kill, but several slashes to the torso should open enough arteries to make them bleed out. A stabbed heart is an automatic death sentence for anything that bleeds. I couldn't separate any limbs (started with a silver sword), but a cut-off arm or leg can also cause bleed-out in addition to crippling your enemy. Throwing can also even the odds. If you're strong enough, rocks can easily break bones, so stock up before a major battle.
Or you could just bring companions, let them charge ahead like idiots, and then attack your enemies from the side or back while they're distracted. You get a bonus to hit chance and possibly damage if your enemy is currently fighting someone and you're behind/next to him.