You all have great points here, and I admit in my original post, I forgot to include the first, and even more important tactic than fighting: While you are fighting, you should be occupied with trying to get away from the danger area ASAP
Yes, being in the middle of a pack of feral hominids is perhaps the worst place to be, especially if they have weapons too. Silver screen badasses want you to believe that the hero can whip down a whole army of assailants, but the screen of real life is anything but silver.
But if you take down an assailant while you are running, you will place some distance between you and the rest, and the rest, perhaps the weaker stomached ones, will give up first.
Imagine the gang in the video chasing the guy at the end. Now imagine the victim choosing this time to produce a knife and neautralize the attacker that is gaining up on him. Attacker will fall, and the rest, catching up to the body, will see their dead or dying friend, will probably be struck by a momentary shock...the "This can't be happening to us" attitude.
THose who choose to continue the pursuit, the victim is still running, and is more than capable of neutralizing another threat if it comes too close to him.
REMEMBER: the elephant and the tiger. The tiger does not bring down an elephant by standing ground and biting, he would be trampled in less than a heartbeat. The tiger is always on the move, striking where he sees is vulnerable.