well, Rafaela and Luciela were supposed to be like Alicia and Beth but they didn't work because they weren't twins. So if each of them has the power of an abyssal, don't you think a combined form of the two would be even stronger? Even though technically Luciela is dead and Rafaela's mind will have taken over, the strength of their two bodies will be stronger than one alone.
And Rubel... well that was unexpected.