B) Would bump it out of the bottom 10%
But then we would have a different bottom 10%. Wouldn't we have to fix that next?
If we keep doing it long enough, we eventually get to a place where all cards are exactly equally strong. Which then largely turns the game into almost pure luck; because it doesn't matter which strategy or cards you go for.
Since a flat power curve is impossible, striving for that isn't valuable.
What could be reasonable is figuring out a minimum power level, and buffing the cards below that so that they are more interesting to play with.
That might be the bottom 5% (about 15 cards) or it might be the bottom 10% or whatever. Whatever you define it at, there would be a place to stop without committing to an endless process.
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The mobile game, clash royale, has one of the best power curves I've ever seen. almost every single card in the game has a place where it is viable. even the 8 starter cards are strong enough to be useful after you've played thousands of matches.
yeah, there are some stinkers, but mostly those are cards that would be unfun, or too luck based, if they were tier 1 cards. For instance, one card, the pump, was nerfed so that it would fall out of competitive play where it was messing things up, but casual players still get tons of value and fun out of it.
They got to this point by knocking down the high spots, and filling in the low spots every few months over 2 years. It might be an continuous process, but the game is better today than it has ever been, and they certainly do not commit to buffing the bottom 10% every patch.