Ok here are some issues:
1 level of ability!? at least make it 3 (1,10,20)
if u leave lanes alone, units will gradualy push there way back and foruth, sometimes gathering a force large enough to destroy the towers.
Towers cant see invisible units...
There is nothing guarding the command tent, u can go invisible, walk up to it, buy from the enemy unit merchant, boom...
Last but not least, 3 heros? agility, str, int. no other heros... you should make 9 or so for each side, so u dont get 2 of the same unit every game.