1) Castle Archers shoot too far.
2) The ability to destroy a damaged wall and rebuild it is overpowered; a player well armed with archers can slaughter an army right before the wall is destroyed, then rebuild it right afterwards, and you have to repeat the whole thing over again.
2) Send Speartans supported by Archers (especially the fly ones), i destroyed 2 walls fast with that, then i sended 2 giants and the Tower Archers killed both before i could destroy the damn statue. Its is obvious that Tower Archers are OP, even if the enemy is garrisoned and already lost you have to bring a big army to pass trough them, or wait for the 10 min end.
Try to win before that massive army appears. Only go that far if you KNOW you can out control (and you have better unit compositions) than your opponent.
Hey i just took all the Gold upgrades at the beggining and created lots of miners, then i attacked and won all the skirmishes, then i was stopped by the method above, i dont like what happened then because i kill lots of enemy unites and keep mines (garrison to heal) but i couldnt kill the enemy miners due to the barriers, so i won all the battles (and sieged the enemy after middle map) until the 10 mins passed and it turns out that his armie was really bigger than mine and i lost :(
In all the other stuff this game is so astonishingly awesome that if i happen to become really good at this ill no doubt in go Premium (it is pointless to be a premium n00b :P)