RenhetEDIT: Didn't a meeting with Valve conclude that they don't like 6v6 because it's stale and unchanging? Meanwhile the Dota 2 meta is changing all the time. I don't think banning a weapon after its first real go is the right way to handle something if we're serious about, well, getting taken seriously.
it isn't reasonable to try to compare Dota's changing meta to TF2's stagnant one. heroes in Dota are much more diverse than the classes in TF2 (and the weapons for those classes), so there's plenty of room for adaption. TF2 is limited by unlock balancing being wonky all the time, so while it is a legitimate complaint that the game gets stale, it's a tough thing to have control of with balance to team size in mind.