Remove the Surrender Function
I have played both League and Dota for quite some time now. And I would prefer Dota because it doesn't have a surrender function. This promotes positive game play because the players know that they are going to be playing the game all the way through to the end so they might as well try. Whereas in League, once someone thinks the game is over, they stop trying and ruin the game for the rest of the people that are playing who think that they still have a chance.