So you know the cards you get after a match, saying who did the most healing, or who killed the most enemies?
In my opinion, you guys should add more cards. For example "Most Resurrections" would a good one to start with, seeing as rezzing teammates is a quite crucial part of the match, especially after the addition of the newest merc - Guardian.
On topic of Guardian, she's a support merc, yet unlike all the other support mercs, she just does not have any post-match cards to give the player any recognition if he/she does really well. My suggestions would be "Most Resurrections" and maybe "Most Projectiles Destroyed" to start with.