Which 6* to r2

Stark78Alfa

I have just 2 5* r5: Domino and Hyperion. I'm about to form my second cb5 but I think maybe it's time to invest on 6*. Here are my options of 6* and 5* worth to rank up and I'm asking for your opinions and thoughts.

Where am I in the game? I'm cavalier, but have Act 5 and 6.1 to explore. 6.2, LOL and Variant 1 and 2 are untouched.