Is a reduction in number of kills a very good metric really?
Is it possible that the new GV system makes it easier to break spawn camps? If guys aren't getting killed, reupping, getting killed, reupping nearly as much because spawn camping is harder, that alone could cause a reduction in kills in a given tour without an actual reduction of people playing in GVs.
The fact that there has been a reduction in number of GV kills, if this reduction is due to the changes, show in my opinion that the changes were for the better, for exactly the reason you say.
The previous "super zoom" tank sights and the spawn-camp "whack-a-mole" slaughter are the biggest thing that kept me out of tanks... I enjoy tanking more now, just because not only is it harder for me, but it has taken out of play some of the BS you previously had with the super long-range 1-shot killers.