Okay time to give my 2 cents
Out with old in with the new. That sounds harsh but it's reality. But, I do miss the Vets. (some of them anyways.)
Talim- I don't really understand why they decided to let this character go...I really thought she would make it into SC5 but then again maybe that could be due to time constraints or they're saving her for SC6 (assuming they make SC6) I do think they will put Talim back in Sc6 considering how popular she was but then again if popularity was the rule then we'd be flooding with fan favorites (ex: Li-Long,Hwang,Setsuka,Mina etc). She still has alot of potential for growth and gameplay wise I would love it if they geared it back to her SC2 way. Only time will tell with this one.~

"
Wind...Guide me"
Yun-Seong- I can't really say much about him he never really appealed to me besides aesthetically. I'm going to be blunt but to me he seemed a easily forgettable character. He never seemed to have much impact on the fans...not like Hwang anyways. If they bring him back well goody for those who like him~

"
Let's go!"
Seong-Mina: Okay, this girl is really charming. It's just her whole personality and her way of being~It would be nice to have her back but why would she be back? You cant just bring back a character and say "oh we brought them back just because", she would need a purpose to be back. In the previous games her purpose in the game seemed to be to follow Yun-Seong or whatever. Same thing with the other missing characters.~

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I won't be beaten so easily,you know"
Cassandra- She'll probably come back in SC6 as the 2nd S & S user, assuming aPat is Pat's "real" form and if they decide to follow the tradition of two S&S users. Besides they'll have that whole "she was in Astral Chaos" excuse to bring her back young and kickin'~

"You can't beat me!"
Sophitia- She's dead..and we have Pyrrha so...~

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As long as Pyrrha is safe, that is all that matters."; u ;
Taki- Wouldn't mind seeing again,after all we don't really know what happened to her and I'm really interested where she went off to and why she did.~
"You're too easy to beat"
Rock- Do we really want him back? ._.; ~

"
Come, I will take you on."
That's all I wanna say about that~ :( sorry if I insulted anyone >.< it wasn't intentional