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It actually much tougher to create a "fair" bot than one that is optimized to win. With the number of different battle modifications, size of hand, splinters its pretty diverse and there won't be statistically significant line up that you could put together to make it even.

As an observation, when calculating odds of winning a lot of the simulators will calculate results of 0 percent or 100 percent. You will rarely get a 50% result which is fair.

Also "fair" matchup requires knowledge of the opponent. You can do this based their % win rate for the last 50 battles which in my opinion is not statistically significant or their actual team submitted which has different problems.

They would put x amount of Ghost Cards on an account and then let the different services run the accounts. They can add more or remove cards as needed so they will stay in the desired rating range.

I hope not. They have the ability to make any kind of teams they want, so you would think their goal would be to make the players happy by providing not only different strength teams, but also much varied play styles to add interesting combinations.