I think that there should be an indication as to how many leavers you had in a game when looking at your game history.
Maybe a circle with the number of leavers.
Because I almost just had the best game I have ever had with Karthus - I had no deaths, then 2 of our players leave. Even though we had the other team down to just inhibitor turrets, while we had all but 1 turret still up.

I tried to /surrender because I knew we weren't going to win a 3v5 match.
But instead of a perfect game with no deaths, I ended with 20-12-11.

I could have gone without a single death but now it looks like I fed the other team.
I wish they would show that we had 2 leavers and that was the cause.