I don't think intelligent creatures would act like that, turning their backs to other enemies to insist in a fallen one, but some creatures would. We need to observe if this is a general behavior or if its only present is some species.
In the case of zombies and other flesh-eater mindless creatures is not so unreasonable to think that they will "hit" a fallen character until someone stops them, thats what zombies do hehehe
You mentioned worgs, I know that its mechanically hard for us, but if you watch violent dog attacks, large groups of people kicking and beating the dog with sticks and even metal bars sometimes are not enough to make it give up on its victim... MANY times someone needs to shoot the animal... I dont know if the same applies for wolves, this matter of animal behavior is really complicated, but again is not so unreasonable.