Consider the normal distribution as an analogue. The higher the sample size (wishing wells) is, the lower the deviation will be. Variance is inversely proportional to sample size. But I think you misunderstand, I'm not actually talking about the average, but the law of averages (or rather, the law of large numbers). It was not my intention to get into a discussion about statistical details, my point was simply that having a lot of wishing wells makes for a reliable card drawer. It may have a low variance, depending on your deck. The more wishing wells you have, the lower the variance will be. And it isn't really fundamentally different from any other way of drawing cards, like chaining villages and smithies, which also is dependent on luck in some sense. It's just a different dynamic.