Autofill Increases Queue Times
If I am not mistaken I believe autofill was created to reduce queue times because there are certain roles, such as support which are not as popular and others, ADC and Mid, which a lot of people want to play. However, I don't know about anyone else but I am definitely willing to wait a few more minutes to get the role that I want. Many people prefer a particular roll and despise, or can't play others. With autofill active you can be thrown into a random role you did not choose or a role you aren't strong in and this leads to a lot of dodging in the queue. So while autofill may decrease the initial wait time it takes to find a game, I believe it increases the overall wait time when you factor in players who dodge because they didn't get the roll they wanted. Granted with higher queue times people may get frustrated and dodge if they didn't get their first pick, in which case I think you should increase the time penalty to 10min for queue dodging in draft and maybe even have at 20min for ranked. There will still be the problem of not enough people queuing up in roles like support so have minor rewards such as an IP boost or 50 extra IP each game you play support or fill.