Objectively, you are absolutely right. The problem is, no unit looks good when compared to the frog. Life is cheap, but it is a completely ''passive'' element. It has no PC and the only CC is the spine carapace, which is arguably not the best since you re usually dead at the same time the enemy units die. Life only has rush and healing. It is not totally objective, but I think it was meant as a balancing factor.
The graviton mercenary is absolutely worse off, so if any unit needs help it is this one. It has defence, but no one uses a unit wit this low attack. Even the mummy is better.
Based on the other units, I say it is not that bad. The crawler is a bit more expensive, but a tough critter that can draw some CC.