The biggest gameplay flaw I've seen so far is the fact that battles are quite boring. Here are two things you usually do:

1) Fight creeps. If you are the TB then one ability will finish all creeps off quickly, if not than this is a chore of micro-managing your DG clicking on each enemy to attack or w/e (at least the rook has a ranged melee attack which can hit enemies "nearby" not like the oak, vampire, or undead thingy who must be told exactly which enemy to hit and often stand there looking dumbfounded (bug).)

2) Fight demigods. This is where the fun should be, but its pretty linear. You do your "thing" vs the demigod. Either you kill him, or he runs off, or you run off, or you die. Nothing exciting. There is no strategy, no trying to corner that DG by using the creeps to your advantage. (creeps usually cause nothing but poking damage to any DG, I expected there to be real danger from creeps where while its usually a stalemate vs two sides, creeps are not just pushovers.) In DOTA creeps helped the enemy hero kick your ass or vice versa, you position yourself using creeps as a moving wall, while trying to disadvantage your oponent by eliminating their moving wall.