Rank-up Dilemma , Which star champ to raknup?? Bg Defence

Asher1_1

6*need R5 + Asc . I just can't pull 7* good defenders , i have some they need Duped to be good.
with T6CC so short if i rankup a mystic i can't rankup any mystic for next 2 months

Sarvanga1_

I have all 4 champs - domino, killmonger , korg and attuma as unduped 7 stars.
I found that unduped attuma and korg get destroyed pretty easily but killmonger and domino still are annoying on defense.