Don't even need to look up to know that they will very likely die to the Berserk challenge.
On a more serious note though, none of the "SS" are center pieces, more about helping others.
Ella, ID and Lemonade all are for helping other to do their jobs, not saying they're not good though.
I suppose Khan is there because of her Exclusive Equip. Good, yes, center piece, no. If anything the center of Horde team is Camel (yes I know she's used elsewhere as tank, but still, SS?).
Titania is for farming, and that's about it. You rarely ever see her in an actual team, not when Glacias is around.
Eternity is arguably the only one that fit to built team around. And she's also known for bricking to anything with damage reduction.
And no LRL in SS, seriously? Someone clearly never AP locked the whole enemy team before.
Moving to S.
Alexandra -> see Titania.
Anything with Fire damage -> virtue of being the weakest element due to not having 'Wet'.
The only reason I can think of for Dryad and Harpyia to be here is that the maker saw them once in last event ex.
Kaen: have you seen Zero?
Safety: she's cheap, I guess?
Mery: I recall using her with Glacias, but that's when Glacias was bugged and didn't work with Rhea.
Ramiel: You want her to use her A2. She doesn't want to use her A2 (or doing anything at all).
Tachi: WTF? Just WTF?
Hyena: Have you seen Talon?
Saraqael: If it was her before the "buff" than you can make an argument for A.