To put it simply, for the Vanguard I don't care whether your Defense is one or ten, I just hit you with an Attack of eleven across the board. As for calculating what kind of attack to use against what kind of enemy—calculate my ass, I just go in with a saturation strike; if you're dead, I win, what's there to calculate.
Naturally, in this situation, even with everything invested in Evasion Defense, the Fourteen Combined Legion still got nearly a thousand men taken out by that volley of Kinetic Arrows. And that was only because Benito was experienced, battle‑hardened, and didn't dare tank it head‑on, relying entirely on evasion. Otherwise, this one wave might have left the Fourteen Combined Legion half crippled at the hands of Sheni Pei.
