Why are characters banned in tournament play for DotA-likes?

Why are characters banned from DotA-likes in tournament play during selection? Are there characters that are actually imbalanced; why not just balance them?

If it's just for the sake of another level of meta-game strategy, then where did it come from?

No, this isn't related to balance, and is actually strategy related.

The origins of banning heroes comes from a match type called -CM, or Captain's Mode in DoTA. In Captain's mode, teams take turns banning heroes they don't want the other team to use whilst picking their own heroes for the match. One person from each team (the person in the first slot) is the one who makes these decisions, so you usually only play CM with a group of people you're familiar with since it requires a lot of coordination.

In professional level play, this becomes extremely important as you want to prevent the other team from picking heroes that they are adept at, or countering the heroes you picked.

For example, say you wanted to go with an "all push" strategy that relies on pushing down lanes to end the game fast (with the drawback that if you don't end the game early, the other team will easily overpower you over time with their "late game" heroes). Your team will probably want to ban any heroes that can counter these pushes, or easily kill their heroes.

While balance/imbalance can certainly have a factor from patch to patch, professional level play sticks to a version of the game that is considered "stable" by the community.

I would see it a different way.

DOTA like aren't about personal skill, they are all about TEAM WORK. This meaning that champion selection is part of the game, you are already building your strategy.

Now, every strategy has its pros and cons, banning can be done in two ways :

• Offensive : You ban champions would nicely fit the opponents strategy, trying to force them to take a "not so good" hero for them.
• Defensive : You ban champions because you now the opponent plays them well, because you don't know how to handle them or because they would be good against your own team

It is true that some Heroes are unbalanced (that's why Rumble kept being banned in the first season LOL tournament), but it is more about strategy than getting out the OP champs.

Example : During LOL first season tournament finals, Fanatics banned the three heroes team AAA used most for jungling. It wasn't because they were OP, but it forced AAA to choose a "second hand" jungling hero that they didn't master as nicely as the three that had been banned.

Without disagreeing with everything that has been said here about how to ban and OP/UPness, you were originally asking for the 'why'. I'll interpret that as "why have the game designers introduced this mechanic?"

And I think the answer to that is quite simple: to raise the challenge for pre-arranged teams by adding a random component. Without banning, a team could just agree on one set of champions and a certain strategy before the game. With banning, they have to be more flexible: they need to practice more than just champion to perfection and they need to be able to communicate and adjust their strategy as they go.