Unless you're going solo you should have your teammates to hold them while you attack and back off when it's not safe again that's how all adcs play except graves and urgot. You have to rely on your team though.
However I can see issues if you just have a pure damage comp like a non-tank/bruiser top laner, assassin jungle, and assassin/non-utility burst mage mid and a damage support in those comps I'll say that positioning won't work since they'll tend to leave you alone half of the time.
But to get good positioning try to examine your teammates and suggest one of them hold their cc-skill just to fend off someone from you. And don't just try to maximize your dps even if you could get off 1000 autos it's safer to just get 1 and move to reposition until you're safe to get another.
I'm also sorry if I sounded too rude just that I do believe the qss will drastically make some champs too strong and yes it can be a nightmare for adcs however I feel that hurrying to complain about it when there's other alternatives to avoiding it is too much of a kneejerk reaction. Unlike the xin buff they're probably going to do compensation nerfs immediately before the patch even releases and again there are other alternatives to avoiding it which also improves building from being too much of a 1 trick pony to what do I need to get like it use to.