The pentalty for playing lost causes out is worse than the penalty for dodging or leaving

Then use smart dodges in champ select. If you can see that your team comp will get destroyed by theirs or if someone picks a horrible off-meta, take the 3 LP loss. It's better than 20.

So if you want to afk in a match and it nets you your first leaver-buster, that's a low-priority queue of 5 minutes for 5 matches, plus queue time.

That's at least an extra 25 minutes, so yes, you're saving 5 minutes in the 50 minute game.

Additionally, your account is now in bad standing, so when shit gets real and you gotta go save Hank or Dean, you get hit with another penalty.