Clinzk can get fat pretty fast - however that doesnt make the game to end. Combined stuns + dust can take him down easily,especialy if his team isnt cooperating.
Backdooring rules make sense. I experienced games which were pretty balanced - I am talking about 80 minutes when all heroes have their inventory full and the game is still not decided. In these situations u dont need clinz/furion any hero can take down buildings pretty fast. And it can be nasty - creeps are at enemy base,but you loose wood fight and enemy hits directly for your towers ....