As I was playing around with the new variant bosses I found myself in a state of insecurity. Since I've finished act 5 and really don't want to 100% it any time soon, whatemagunnado?
For reference, my humble roster:

Now I can take any of ny R3 5*s to R4, but I'm not sure it's a good idea. Sure it's fun, but i dunno.
In case none of those options seem appealing, here are the rest of my 5*s: