When you are queued up for a match and someone leaves I have a pretty strong, passionate dislike for the fact that I am automatically queued up again right away. For two reasons;
One, if in that brief couple of minutes I realize a lack of expectations for my team (since usually there are ~3 repeat team mates), I can choose not to queue up right away since the chemistry wouldn't work.
Two, A LOT of the time, I get put into matches with people who THOUGHT their game was going to start so they went to expose waste, or made a snack, or did laundry, etc. And then I have to go through the process of choosing champions all over again for a game that will either never start, or start with a random champion select mistake. Not to mention nobody was banned in ranked if the captain is the afk person.
In addition, I have been unfortunate enough to find my way to the cursed ELO of around 1000 where people don't grasp game mechanics as much as others. (In my defense a lot of losing games I finish with a positive score). So I find that part of ranked games is luck of team selection. But I digress....
Please eliminate the auto-rejoin mechanic, because the reasons to remove it, far outweigh the reasons to keep it.