Most of the time, if one side is higher level by a couple of levels, its about game over. They can beat you straight up, hold lanes etc. Also in alot of cases they can have alot of kills with zero deaths. The game is all but over.
What about a way for the other team to catch up. For example a Reg sniper player has 10 kills with zero deaths. He has earned 10K in gold. So not only he will be higher level, he will have better equipment. Might as well concede at this point, since just wasting time and prolonging your defeat.
Implement bounty system siimilar to other games. So the Reg sniper example, every kill he earned, he would also gain a 1K bounty plus xp. So if he has 10 kills with zero deaths, his bounty would be 10K plus xp. XP depends on level difference. If the Reg is L10, and the DG who kills him is L8, then more XP then if the other DG is also L10. That gives the losing team a chance to catch up if they kill him. If he dies by a tower (suicide), every one on the other team gets 75% of the bounty reward. This gives the Reg player more caution since he has to be more defensive.
Right now, if the other team is higher level with alot of kills rack up, game is over. Very small chance to catch up. Not suprisingly rage quiting and large number of disconnects.