Exactly. You can't argue proportionality on effectiveness. If Hamas fires 1,000 rockets into Israel and kills 2-3 people and Israel retaliates with one bomb and kills ten, that's still proportional by most people's standards.
Maybe Hamas should get better at killing people, because if you look at the straight up number of times each side has attacked the other, they portray a far more even conflict then basing your logic strictly on death totals.