Lower upgrade mats in higher tears in Coliseum

I have a problem with MK 5 Cresh Ability modules in Coliseum rewards. I am doing t7, all my characters are lvl 70 except Asajj who is left at 52 because I cant level her due to the fact that I do not get any mats fot her. Whars the Idea here?

Crystals only? Why should I play coliseum then if I cant select the tier where I get the mats for her?

Thank you,