The biggest lack of counterplay.
Surrendering, Now don't get me wrong, it's definitely useful but it needs to be extended by 10 minutes, people give up far too easily, give more time for people to consider it, I'm sure we've all had games where we're doing fine and then your team surrenders only for you to think ...?
Now I'm not saying increasing the time will stop this but it will definitely allow people more time to think instead of just giving up, in most cases the outcome of the game isn't decided around 20 minutes unless it's a stomp in which case the game would be ending soon, the idea behind increasing the time it takes to surrender is purely to stop people from giving up so easily, and if you say what if the enemy team isn't ending? well then that just gives all the more chance to come back, surrendering is vital to the game however people giving up so early on is really bad and I've lost games we should of won simply because people didn't play it out and give it enough time, making the surrender vote at 30 (which you can normally tell if you'll win or lose by, will help because let's face it, at 20 unless you're utterly getting stomped it's really hard to tell and if you're getting stomped that hard then you can't expect it to go on longer without the risk of enemy team throwing.