Well EOK gives a LOT of aa and the aa experience per kill scales down as aa totals go up. Other expansions did not increase aa as much as this one so the slow down of aa gain as you get more aa is more dramatic. That may or may not have something to do with what you are experiencing. Assuming you measured your aa per kill just before the patch and then right after. As above though you may have passed a point where your aa gain dropped due to the curve.
