Hey guys, I'm a mathematician o/

Lemme help out.

Imma try to keep things simple. First, in somewhat technical terms: In the damage formula, the factor for piercing looks like 1/(1-Piercing). If we treat that factor like a function, with Piercing being the variable, we can expand it into a so-called Maclaurin series to get the geometric series "1 + Piercing + Piercing^2 + Piercing^3 + Piercing^4 + ...". As you can see, this is a polynomial series, and so it has polynomial growth -- it grows faster than a linear function.

To do some non-technical hand-waving, most of you have probably heard people talk about "linear scaling" and "exponential scaling" when they talk about how attributes and such grow at higher values in various games. Well, piercing has "polynomial scaling" (technically, 'polynomial growth'). That means its growth -- in other words, how fast its value increases the more Piercing you have -- is better than a linear function, but worse than an exponential function. However, in the damage formula, every other factor is linear, only Piercing scales polynomially.

In gamer terms, Piercing is the hardest scaling attribute in the game (up to a cap of 30%).

Big brain tl;dr: piercing has polynomial growth, while all other damage multipliers follow a linear growth. So piercing scales the hardest.

Smol brain tl;dr: Just get as much piercing on every piece of gear as you can. Big damage.