I’m mid 4* transition with maybe 12 4* champed and I’m not sure who to start ranking among my 5*s. I’ve read you should co-rank two of them so as not to throw off scaling so the candidates are…
Silver Surfer seems like the best bet to start leveling in that group. Phoenix is best when she has 4 or 5 purple covers, and OML without black is pretty pointless. Try leveling Surfer so that he’s at the same level as your boosted 4*s, that should keep him from killing your scaling and MMR.