similar sort of things kept happening to me when I tried to play with friends, in the end we didnt play for long

Parties are really meant for the matchmaker, but neither matchmaker nor Teams should make unbalanced matches. That's why you'll hardly be able to play with another top player in a party in small teams.

Big teams should be more reliable in keeping parties together, as elo equality can still be assured by juggling around unpartied players.

What would you want the game to do? Creating even less balanced matches is surely not going to be of much help.

I'm guessing the balance in this game was made strange by the two very new players, the numerically uneven teams, and possibly other parties.

It does seem odd that Team 2 is predicted 66% to win when switching Shaman and Znack would (probably?) reduce this discrepancy. Perhaps there is a bug somewhere.

Perhaps the chances shown here should display both (either to admins or to everybody) to make resolving questions like this easier.