Autofill leads to the most frustrating games I've ever had.
First of all, autofill was originally created to force people to play support to reduce queuetimes. But then why the hell aren't people who specifically queue up as support immune to being filled?
Second of all, it doesn't do the job it was intended to. If you could count up all the seconds you wasted because people dodged or fed, you'd end up with a lower match quality and a longer queue time.
Third of all, I play your game to enjoy it. Taking player agency away and replacing it with "You'll probably get the role!" just makes the dodges derived from your autofill system all the more annoying, because next match, you could get support. Could.
Just remove it already. It's a shitty idea. Encourage people to play support by way of like, IP boosts or more fun support champions a' la' Rakan. Forcing people to do something like this will never end well.