Just my opinion.
But i think that the answer to that isnt in the surrender time.
Most of my friends have at least 1 game like these per day, generally more (i had 3 yesterday, and 2 today).
So, i think that the punishment for the ones that leaves the team, should be more severe.
I liked the changes in the leave status, but it is kinda too soft, today i saw a guy with 153 leaves, leaving another game, and most of the players in that game already had more than 30 leaves. That is way too much.
I also see a lot of games there one player just stays in the base dancing or whatever. I report those guys every time, but they keep appearing.
What Riot says about being more severe with those kinds of players?