I'm pretty sure you're right and I've been doing that (quite a bit on heroic lei shen as I knew exactly how many cds I would get in p1 and p2). I mean if your KS (should you use it now) will come off cd 20 seconds after AR, you could delay it 20 seconds easily to get a better insight because when that AR comes, you will burn probably a minute off your cooldowns allowing you in either case to KS at the earliest when your AR finishes.