Yo!  Here's my 4-person team review because it's just preferential:  Ami, Vera, Laka, Oalston.

Ami is my 1st slot MVP because I've a love for Blue Mages in any Final Fantasy game despite how glass canon or OP they can be.  Ami is just that girl who can buff your party, destroy single-targets and STEAL!  I love using Big Guard, Bad Breath, Sickle Slash and Maelstrom because that's all she really needs to dish out Blue Mage power onto foes in any random and BOSS fight!  Big Guard is the best utility dating back to FF5 well...because protect/shell is a must AND it introduces 10% HP increase to the party.  It's still utility even though HASTE is removed but another character fulfills the party boosting, respectively. Bad Breath is the status ailment blue-spell I often use from the start or secondary cast onto bosses because most are weak against it; hello halotosis hhhhhhhiiii.  So!  When you see a boss struck by STOP/STUN and crippled by SILENCE/BLIND, yea you can win even if the damage output at 800+MAG is approx 2500-4000, I'm not mad at it: it's meant to annoy the enemies, not be a killer blue-spell.  Sickle Slash is Ami's Genji Glove blue-spell and when it lands, I tend to kill that single-target at 20000+ damage...BUT if you put on the Sniper Sight relic: MWA HA HA HA death becomes that target, but do you REALLY need that exploit?  You can better use other relics for the relic spots.  And Maelstrom, the water-element with STUN status is situational because only a group of enemies are immune: sea creatures; why would I water an octopus to heal it?!  I just consider it a diet-ULTIMA spell with bubbles spray...  OH!  Yeah I use the Mimick Stick if I'm feeling adventurous because assigning Ami as a secondary stealer is fun: maybe the farming is faster, maybe it's useless; my Ami build with nethicite bonus cycles, Golden Apple eats and some Miracle Fruit chewing makes her so lovable to use in this game!  Here's where the Tetra Elemental shines onto Ami: she is the first slot for all incoming elemental spells cast from magic bosses/enemies.  At least in my gameplays, she always absorbs those four elements like the Avatar she has trained to be.  Finally, food for definitive thought: put the Ribbon on her and nothing will stop her from dancing blue-magic to annoy the crap out of the bosses' underwear!

Vera is the assigned 2nd slot character in gameplay that is the last to cast espers to primarily clean house if I'm speeding through or buffing the party if I'm being lazy or healing effectively because it's strategic; the Almace hammer-type 250MAG made her 1000MAG.  I use only a handful summon in a casting cycle to keep her essentially busy: Bahamut, Alexander, Odin, Kirin/Starlet and Shemhazai in that order because the first and last espers mentioned have a cool down of 5.  Again at 1000MAG, Bahamut-breathing obliterates everything and chips damage bosses rounding out at 35000 because it's non-elemental based.  Alexander boasts an elemental HOLY whiteout to the undead and dark affinities which variably skyrockets from 29000 to 65000 damage because of it's type.  Odin has that cool auto-DEATH percent 45-65% so for 1MP more than Alexanader AND non-elemental type, Vera can mince everything to pieces when it lands otherwise the damage cap for me is usually -9000 less than Bahamut.  Kirin/Starlet: need I say anything?  Kirin heals 2000HP plus adds REGEN to the party while Starlet heals 4000-6000HP randomly and still is your best healing summon Vera could ever wish for.  Lastly, Shemhazai...Vera's Bad Breath esper with very low damage use but is capable of acting like a multi-status attack onto susceptible targets is nice add-on to me after Ami's blue-spell.  So we get multi-person status ailment usage!  RAWR!  Equip her with Eidolon Dress to take advantage of the -40% MP cost because you can better fit her relic slots for strategy: give her the Ribbon and a relic that will EITHER boost her MAG over 1000 (because you don't need to cap her out at 2000...do you really? LOL) -- I give her a Geomancy Ring because of the -10% incoming spell damage no matter what element type it is...kinda like an Elemental Eater but with other stat-build buffs stacked to it.

Laka sits in 3rd slot because why not?  I focused mainly on maxing out her VIGOR because the VIRUS spell is her best magic attack rounding out at 8600-9999 damage and it's ALL enemies!  The Gladius knife boasts 720VIGOR so your shards-apples consumption can be given to whoever other physical damage dealer you want; I choose YOU Laka...WHAT A STEAL!  Har-har yes, I let Laka STEAL anything and everything from every battle whether if it's dummy Lambchops to shard/apple farming to x99 Elixirs. Plus she's inherently the fastest so wisely I can either STEAL or cast HASTEGA to complete my party buff early on.  Slap a Bone Belt onto her to benefit the VIGOR boost because you can just feed her the Speed Shards and speed-bonus cycle her with Yiazmat and/or Cihuacoatl...beware of Zorigami nethicite because your MP is permanently reduced unless you counter this aspect with x99 Mana Shards to maintain the bonus cycle crippling.  Ribbon is a must, come on now?!  Don't sleep on Laka.

Mr. Oalston my archaic tongue black mage is the 4th slot and the magical human weapon of mass destruction.  I build his MAG stat to 2000 using the Laevetein/Lordly Robe equip set up plus Faluhd Relic - what more could you do to him?  Oalston's main offenses should be Meteo, Apocalypse and any -aga elemental spell.  Meteo hits x6 at 10000 damage per so the total kill is 60000+...yeah the boy is a murderer. I never really levelled him up to 99 to get Ultima because...meh I just did without it.  Apocalypse is earth-type so anything flying/floating or earth-resistant won't succumb to the 19999-23000 damage it tends to dish out during battles.  Besides Vera, Oalston is another speed run battle killer for all groups because using any -aga spell for me is 9999-22000 digits.  Oh yea, give him the Ribbon too so he can be like one of the girls being the only testosterone on the winning team.  Jokes everyone.

Everyone else is meh; do I like them?  Of course.  Do I use them?  No not really. 

There is a lot of other characters who has potential to do good damage
lyric deal 24-28k damage per turn with the right luck build and with wild gambit (found on tower of babel), siegfriend deal 8-9k damage x 4 and etc, overall this game seems to have more good characters than bad ones, sadly there is definetly some ones i would rank as bad or not worth the effort, moguel and boshe being examples.

I mean I did BEAT the game with an all-boy band team...LOL.     So YES you are RIGHT, you can use a different diabolical team to beat THE END BOSS up to a pomegranate pulp.  This one was more challenging than an all-girls plus Oalston MAGIC based endgame team. 

Vahn being in the 1^st slot is THE SHIELD of the team; I slap on the Tetra Elemental relic for him to soak up all the spells thrown at him AND equip all the Genji equipment minus the Genji Glove because of the HP + MAG bonuses.  This setup ensures he is always hit first, absorbs any of the -aga high tier magics and is capable of healing everyone with Reis Wind for 5000HP+ being the 2^nd to cast spells when needed.  Use his Dragon Strike often as it lands 25000+ damage and is the 2^nd dealer equal to any magic-based ally used before.  There’s nothing more to it: Vahn is the killing defending healer machine, word up.  Remember: Ribbon his butt up.

Siegfried in the 2^nd battle slot is my favorite to use in this all-boy band team because I ONLY use one technique ever with him: FLURRY!  Spend all your power shards and wisely rotate Yiazmat for +5VIGOR bonuses on him to get his VIGOR as high as you want.  I landed at 1530VIGOR with Ultima Weapon equipped and his Flurry was 7000+ damage output which rounds out to 28000+ total, outsmashing Vahn’s damage cap.  So that’s TWO physical fighters that rival the all-magic team.  His equipment can easily be softened using Dragon Helm and Dragon Armor because of the VIGOR + HP bonuses making him hard to kill with Ultima spells because of his near 9999HP cap mastered!  As for relics, break him up with Bone Belt and tie him down with a Ribbon.

Godot is crimson at the 3^rd fight slot being the only magic-boy in this team: I like him ONLY for Curaga EVERY cycle…maybe Raise or stick a Stimulant on a slow dude-fighter for miscellaneous turns.  If I’m slacking I’ll just cast Waterga, his only busted elemental spell that hits 9999 damage because his MAG is 2000: use both Cosmic and Infinity Orbs to maximize his Curaga healing, that’s all.  I mean, like any magic-user I’ve used, I equipped him with the Geomancy Ring to block incoming magic attacks -10% and enjoy the other stat buffs the relic provides; his only weak point would be elemental weakness by -25% but it’s moot because his HP is greater than 8500 so he survives even the meanest Ultima tossed at him but will die horribly if a Meteo is attacking him only.  Ribbon him up, ya’ll.  THE END FOR EVERYONE AWAITS!

In 4^th place is…Nobumasa.  The ninja favorite where his magic spells are determined greater when SPIRIT is at its peak or maxed out.  Zanmato is his mainstay sword coupled with Genji Glove to be a free 3-hit monster.  Because his SPIRIT is high, using Yasuragi will enable his triple combo to land 7000+ damage, which translates to 21000+ in total.  Dude, Yasuragi speeds him up, protects him from BOTH physical and magical damage and in turn Nobumasa is the 3^rd damage dealer of this boy-band.  Dress him up in a Vishnu Vest to deter all elemental attacks by +25% resistance and the Euryoky Mask because of the multi-patterned stat buffs designed in!  RIBBON him up for status attack invincibility finally.

Yeah, this team was fun!  I tend to do Stimulants on Vahn, Siegfriend, Godot (or he just flimsily casts HASTE on himself) and Nobumasa uses Yasuragi all on the first turn to be dynamically speedrail faster than the enemies/bosses.  When your MP dries out, use Hyper Ethers or Megaelixirs in case you do something dumb and die in crapped-out efforts.