Of course we should look at mortality rate. However, the paper in question which decided to multiply the kill rates by 5, based that on very long low-intensity wars (Darfur etc), where the war in question is more similar to short high intensity wars.
For example, Kosovo war, which is more similar to Gaza war rather than the Darfur, had basically no excess deaths, and while the Gaza war is far more intensified and ugly, so there are likely many excess deaths, it also likely is not like in wars which lasted for a decade, so I think their/your numbers are way off.