Playing mid lane sucks
It isn't enough just to do well in your own lane. You have to do well in bot lane, too. You're forced to babysit them if you even want any hope to win the game. Honestly, you shouldn't even bother laning. Just take 3 bot lane. As long as you get your Tristana/Vayne/Varus fed you've won the game. I appreciate the fact that this is a team game, but it really doesn't matter at all how well you do on your own. If your bot lane loses, you WILL lose.