Which Mystic Should I Rank Up?

I am incapable of my own choices, so asking the masses:
Which mystic should I next rank up?
I'm Valiant so mostly looking at BattleGrounds and Casual AW as well as other larger content like SoS etc.
I currently have Wiccan 7* at R2 and Absorbing Man 6* at R5.
Key 6* Options are: Dr Doom, Claire Voyant, Rintrah, Morningstar, Tigra, The Hood, Long Shot
7* Options are: Sorceror Supreme, Kindred, Dragon Man (none awakened)
Not listed are any 6* who exists as a Basic 7* (America Chavez, Juggernaut, Sasquatch, Mojo, Diablo, Kushala) because I feel like it's a bit of a waste to rank up a 6* when the 7* could be just around the corner...
Which mystic should I next rank up?
I'm Valiant so mostly looking at BattleGrounds and Casual AW as well as other larger content like SoS etc.
I currently have Wiccan 7* at R2 and Absorbing Man 6* at R5.
Key 6* Options are: Dr Doom, Claire Voyant, Rintrah, Morningstar, Tigra, The Hood, Long Shot
7* Options are: Sorceror Supreme, Kindred, Dragon Man (none awakened)
Not listed are any 6* who exists as a Basic 7* (America Chavez, Juggernaut, Sasquatch, Mojo, Diablo, Kushala) because I feel like it's a bit of a waste to rank up a 6* when the 7* could be just around the corner...

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Comments
Valiant, mostly Battlegrounds focus.
If you want a decent all-rounder, go for Rintrah.
If you just want fun, a unique rank up, so to say, pls pls rank up Loki. I have been waiting for him as a 6* for God knows how long, and he's literally carried me through act 4 and 5. If you want to, give him the full treatment.