This was a HUGE issue for me in Mw2, with the commando pro 10mile knife lunge at 1000000000000000,0000000000000000000,0000000000000000000000 miles per hour right through even a shotgun blast.

I have seen quite a bit of mad knifing in this game too, i can only say its rare enough (for now and in my experience) to not be annoyed at it yet, just try not to throw any controllers accross the room, it will annoy you even more if you have to buy a new one!

It should be a 2 lunge kill to balance it. I feel your pain as ive lost count of the amount of times i put 4-6 bullets from my ACR into an enemy and he still moves forward and knives me!