I dont think theres a definitive stat that stands alone. Truly skillful players will have good ratings across the board (no, im not one of them lol) but for me none of the stats can measure overall improvement and some of us have gotten better with time. Any of my stats make me look awful and i was, but recently ive been much better as ive played more crucible than ever before since shaxx started giving out bounties. However i still suck at elimination which ive been helping a mate with for his quests and so even my recent kdrs will not be any better.