Which 4 Star Mystic should I R4

MrBanks

I am looking for my 6th R4 4* to be a Mystic since I do not have any powerful mystics on my roster.

Krumbledkookie

Waiting for a better champ is probably the best, but if you're dead-set on ranking up (like I would be, I'm bad at waiting), I would go with Iron Fist. He doesn't have the best reputation in the community, likely because he's something of a glass cannon, but he hits hard as hell, and his armor break is outstanding. I love my Rank 4 Iron Fist.