Adrenaline Injector assault challenge PROBLEM.

To me it seems that the adrenaline injector quest for the assault class seems to be miscoded or outright bugged. It only counts towards the 30 kills "While using the adrenaline injector" if you manage to kill someone immediatley after the animation for injecting finishes, leaving you completely defenceless while the animation happens. the only viable ways I can see to successfully achieve a kill reliably is to either have good luck and timing when you inject and run around a corner, or you sneak up on someone unaware and inject for the 2 seconds it takes in inject then kill them.

EA, PLEASE FIX THIS! THIS CANT BE HOW THE CHALLENGE WAS MEANT TO FUNCTION!