Boros Aggro's key threats like Magmatic Hellkite, Nova Hellkite, Smaug the Magnificent, and Clarion Conqueror all cost 3 or more, so Requiting Hex's mana value 2 restriction leaves it dead against their real threats. Get Lost and Pyrrhic Strike give you clean removal for their bigger dragons and Clarion Conqueror, while Dawn's Truce protects your board from a critical mass of burn or combat damage on a key turn. Emptiness's evoke mode for -1/-1 counters is too small to matter against 4/5 and 5/4 bodies, so it's cut for more impactful answers.