So, Kabam originally promised us diversity across all the battle groups. This never worked as intended. Instead, the system was counting each battle group's diversity individually.
Kabam Miike
promised us to fix this.
Me and my alliance were prepared for the fix, and many of us ended up ranking up lame champions just to increase our diversity and rating.
Two weeks later, Kabam has decided not to fix the glitch and leave it as it is. Because of player feedback.
Now I have ended up with r5 Kang and r5 BB. They are no longer required for diversity and for defense, I think we can all agree that fighting these defenders is the easiest thing in the world.

Conclusion: me and my alliance have wasted our precious tier 4 basic and class catalysts on the champs that we will never need. Kabam are saying that they are unable to give us rank down tickets or manually de-rank them.
What to do? I miss my cats so much... Would have preferred to use them on much better, useful champs!