Well since Malik has altered GT, Rigor would be a lot weaker. An accurate estimation of Bills' power is 857 quadrillion. Since GT is altered, Rigor would be at 200 trillion, meaning that Base Goku after absorbing Godly power is 5x stronger than him. In other words, Bills is 4,285x stronger than Rigor. But IF GT has not been altered, Rigor would be at 1.7 quintillion. But Bills gets stronger as well, (his power at least doubles within a year). Meaning in this era, Bills would be 20 quintillion and Whis 30 quintillion
Well think about it. Rigor would have killed SSJ4 Gogeta if SSJ5's strain didnt overcome Rigor's body. SSJ4 Gogeta reduced Omega Shenron to a mere plaything and Omega would defeat Bills with little trouble or at least I believe so.
I understand your point of view! But Omega Shenron, Rigor, Gogeta, etc., can not feel the Ki of the Gods. It is easy for Bills to attack without that we can feel it, that's how it crushes Goku SSJ3 in 2 moves. In addition, Bills are fighting only 70% of its maximum strength in the film (he says himself), so we do not know what he is able to be up (As we have seen Rigor, and Gogeta Omega Shenron to their maximum).