These are all desirable goals. When one builds a deck in a CCG, one has to consider how many of each card to put in. Each possible combination of cards can be considered a point in a space of all potential Each combination will have a value, defined as the chance of winning in a given play environment. For each point in the space of all potential decks, the value of the function is its chance of winning. The best way for us to visualize that kind of thing is to imagine choosing decks from a 2-dimensional plain of choices.
Good decks are the ones high up, on the mountains.
To examine these effects, consider a design decision between 2 different cards. I've put in some graphs of differing situations for the trade-off between the two cards. Good is up. This is the situation that card limits are needed for. Typically, one of the two is better than the other, so there's only one good deck.