There should be a system in place as follows.
Leave the knifing mechanic as is.
If you are currently at 100% health and you knife someone, that should be a one hit kill.
However if you are hurt and have say 80% of your health, then your knife attack should only account for 80% damage on another player. If the player that you knife, and inflict 80% damage on, gets shot by another player shortly thereafter you would get an 80 point assist.
Knifing should still be a 2 hit kill even if your health is below 50%, however if you only get one knife on the guy before he kills you then it should still only inflict as much damage as the health you have. A way to balance this could be to make your recovery from the knife lunge shorter if you knifed a guy when you were damaged, giving you more of a chance to shoot/2nd knife the enemy player after you already knifed him once. Some tweaking with the mechanics could be needed...
Another possibility is that if you knife someone when you have less than 100% health, then the player doesn't die but goes into last stand...just a thought.
This would reduce one hit kill knifing to situations where you sneak up on someone, or quickly knife them when you come around a corner or doorway. In such cases you deserve to be knifed because you either got snuck up on, missed with your gun or knife, or were slower at the knife than the other player. All of which are fair gameplay mechanics.
This system leaves the current knifing system basically intact and wont be as much of a shock as making the knife a default 2 shot kill. Which in my opinion would nerf the knife to the point where no one would use it, and at that point you mid as well remove it entirely. Gameplay in COD is too fast for a default 2 hit knifing system. I hope they don't resort to that.
