I've been trying out the new reward cards one by one, and I can see others are doing the same. The top battle of today had a reward card lined up in each team.
As you can see, my opponent had the Rusty Android, level 4 in his team, while I played the Flame Imp, level 3 for the first time.
It is nice to discover that the cards are more useful than I originally thought. I really like the new abilities.