I get that some people are boosted, but what you're trying to tell me is that you're getting groups full of them, all the time. Because only then leaving a really, really bad group would have an effect on your leaver %.
Who wouldn't leave a group like this? Every decent player would - which wouldn't translate into a higher leaver %. Your leaver % would only be higher if you were statistically leaving many more groups than everybody else. Take more time forming your group, don't group with gray logs/no logs and you should have decent groups, at least most of the time! Or else you're doing something very, very wrong.