I'm in no way great at this game but I'm definitely average. There is nothing more annoying to me than playing super well or getting to the final rounds and then losing in a team game because the match up just wasn't well. I hate team games after losing the past 10 rounds of a team game causing me a place in the finals. That second to last round and I'm out because the team matchup was poorly made.
Another side note... annoying concept is the people who wait around at the end. Just to grab people. I haven't personally lost because of this but I can only imagine how annoying that could be. Those players should be punished in some way.