some of the castes needed speed boosts. Everything except boiler should outrun a marine. before the update a young warrior in agility was the same speed as a fully armored marine. how can a marine keep up with a 4 legged alien. that makes no sense. Things like runners/lurkers however did not need speed boost thats a fact. I dont know why they dont just remove mutators from specific castes to keep from unbalancing things but they dont.