has anyone noticed that the leaver's team usually wins in the tribunal...?
thought it was weird.

I wouldnt say usually wins, but they do win a surprising amount...

Well, depends when the leaver leaves. If its at start then the other team can have 2-3 solo lanes (if jungler). This makes a somewhat shaky early game and a strong mid game. Decent late game and horrid over-time. You can win 4v5's as long as you finish them before overtime when the other team is starting to finish their builds.

If the leave is 10 minute in or so though you'll have a harder time since they essentially just leeched 10 minutes of xp and that could've gone towards a solo lane.

I still tend to see more losses than wins but there are ocassionally a few wins in there.

Often times I feel like the chat log suggests that the leaver's team has lost, even if the info says they won. Whether a team wins or loses generally doesn't affect my verdict though.

I've had reports that tell me their team lost because of the leaver, but the leaver's game status said they won. So I'm guessing it's just some kind of display bug, and the large percentage of these aren't really wins.