Hi :)

regarding those types of fusion 

1- all new rares and epics really make them hard and more importantly it dilute the champs pools with useless rares and epics . 

2-all old rare really make it very easy to fuse , last few events when fusion pop up i find like i have 14-15 rare and 3 epics ready !  way too easy 

so why not using 50% new and 50 % old champs . so we can still use our vault champs and yet still play and compete to end the fusion