if u cant beat story mode i guess u lack of level.. go up some lv on exp vortex.. story mode doesnt need any excel unit to win.. even with the most trash team also able to complete it..

Your team is sufficient to clear current content already

Focus on:
CoD
Bartz
Kefka
Celes/Golbez/Vivi
1 more slot for healer which you can get from story(Fina)

Like JT said, you need to level up and most likely update your gears

celes.. shes 1 of the top supporter.. currently element mage is useless... most boss is vulnerable to physical attack unless u got ultima or comet (non element).. keffka got hyperdrive (non element) so its ok but golbez is pretty much useless.. mage only shine in pvp which we will not be getting it quite sometime..

well celes is mage supporter though.. she will be useful to keffka since celes got focus which increase matk by 40%.. for those 4* max i advise u not to waste so much time on them coz u will not be using them in later case..

yup.. grind all the quest.. grind your team to 5* with exp vortex ADV.. cure i heard they said is base on SPR.. its up to u whether u want equip staff or dmg lol.. my Fina using mace =D
Cecil and exdeath... and yes used up all your available summon to get more char coz currently u only have this 2 for a 5* team.. though rain, laswell and fina could slot up for it.. Fina is the only useful main character for now..
5.. the max lv will still eat up the exp.. so in order to farm exp for weaker char it is better that u add more strong friend which can solo whole ADV exp..

wooow you are fast, i short of material awaken all my heroes ... lolx 

5* Chizuru x 1 (last night try luck spend 500 lapis for current features unit end up getting chizuru ==)
4* Chizuru x 1
4* Exdeath x 1
3* Golbez x 2
4* Kefka x 1
3* Kefka x 1
4* Leo x 1
4* Zidane x 1 (Free ticket from daily entry)
4* Vivi x 1
3* Kain x 1
3* Rydia x 1

above is all heroes i'm gonna keep it... atm only hope getting Garland, Cecil, Cloud of Darkness and 1 more Zidane.

anyone farming rod of gravity?