Looking at the missle, I think it were meant to be an anti-battlesuit weapon. It's got very low crew requirements and isn't encumbering, so it's easier to build a platoon that can keep its speed up, while still getting range that's superior to the MG/SL/Flamer that was the main gun of most pre-Jihad suits. It's not about raw damage, it's about being able to wear down an Elemental without getting chewed up in return.