someone rate my current team :
Squall ( BSB)
Y'shtola ( BSB)
Vivi (BSB)
Sephirot ( SSB)
Raijin ( BSB)
I see two or three others already pointed out "no breaker" but I'll look at it from my view.
Squall, good spellblade. Has a great ice bsb, if that's what you have. I don't have any relics for him, he doesn't get used by me much. Also, in my opinion, the spellblade skills were lacking at the 5star level. However, as you may have read, big changes are coming.
Y'sh is a great healer, great bsb. She's a keeper.
Vivi. I have his BSB, but he has very low hps. Also he is one dimensional black-mage only.
Seph, he has limited utility, however, I have his BSB and OSB. His BSB command 1 does piercing damage and you'll be surprised how well it does, especially on bosses and raids. Also, make sure to hone up Hailstorm Samurai skill. Nice atk buff (with good damage) for Seph. He can also use Dark Bargain, he's one of the few that can stack the two buffs.
So if all you have is a SSB for him, you may not want to keep him. Unless you don't have many other options?
Raijin is a fun character. I mostly don't like monks but I do fit Raijin (have his last stand SSB) and Tifa (have her bsb and it's my only earth) into my groups on occasion. The 5 star monk abilities aren't too hot in my opinion. Meteor Attack and Fires Within aren't too bad.
As the others have told you, you really want to have a Support 4 (all breakdowns) or Support 5 (all breakdowns, plus Full Break) or a Dancer4 (all breakdowns) or Dancer5 (all breakdowns plus Multi-break) I refer to these guys as utility because they can do so much.
What else do you have?
Vivi and Sephiroth are somewhat limited in what they can do. Raijin is also, but maybe less so. Ysh and Squall are keepers for sure.
I say work in a mage who can also do summons or also backup heal/buff. And get you a utility. You may also benefit from having a "tank" .. think Pecil, WoL, Agrias, Ingus and characters like that. They're banishing strike, gaia cross, and guardstrike are good moves. Some of them can even break, some of them can Prot/Shell/Res for you.
Lastly, consider this group of mine. I have about 10-15 characters I rotate around until I find the best mix.
Vaan - Breakdown/Breakdown - Instant BSB debuffs.
Firion - Breakdown/Breakdown - Instant mblink BSB.
O Knight - The only person who can do more is Tyro, but O Knight has godly stats. Seriously can tank, can break, can heal, and can mage like a mach truck.
Relm/Lenna - My clerics. Relm brings last stand, Lenna brings a nice USB buff. They are one dimensional but well healers are.
and usually either:
Alphinaud - Black Mage, Summoner, Backup Healer, nice SSB and BSB
Tyro - Can do anything. Also brings wall and a Prot/Shell/Magic Blink BSB that has break burst commands that stack with everything.
Like I said, I have about another 8-10 I use, but you get the point. You really want to think about it like "Wow! This group can buff, debuff, do big damage, take a beating, and has toys like Last Stand, Blinks, and Radiant Shield"
I typed way more than I expected. Post follow up questions or tell us what else you have, most any FFRK'er likes to "TheoryCraft".