Babylonia Prep and team building.

If you want more straight forward fight, keep using your zerker and Buster playstyle.
About Arts, they're pretty tricky to use.

Here's some of the team comps :
Dragon Slayer team, Siegfried + Georgios + Waver.
Hardcore anti-male, Euryale + Stheno + friends Euryale.
3 Turn Brute Force farming team, Raikou + Waver + Friend Gilgamesh + Tamamo Cat/Lancelot zerker/Fran.
Turtle whassup homies team, Marie Rider + Marie Caster + friend Marie Rider/Caster.
Jojo ora ora ora team, Martha Ruler + Sanzang + Beowulf.
Female Dragon Slayer team, Martha Ruler + Martha Rider + friends Martha Ruler.
Usual Buster Crit, Jalter/Raikou + Hans/Leonidas + Waver.
Stall team, Hans + Mashu + friend Hans/Mashu.
All star Last man/woman standing team, Og Nero + Marie Caster + Chu Alter + Marie Rider + Og Chu/Proto Chu + Friend Hercules.
Guts Stall team, Hans + Mashu + Irisviel.
More Buster Crit team, Raikou/Jalter + Marie Caster + Hans/Waver.
Low HP mobs Clearing team, Raikou + Chu Alter + friend Chu Alter/berserker.
Quick meme ala Kintoki, Kintoki + Atalanta + Waver + Scat. Chaldea Battle Suit MC.
Solo Chu Alter, Chu Alter + georgios + friend Georgios
Solo Nero, OG Nero + same with Chu Alter
Solo OG Chu, OG Chu + same with Chu Alter
Solo Herc, friend Herc + Georgios + leonidas

Not only Babylonia, you can breeze and smurf through lots of challenge and contents alike.
Just need to raise each one of them step by step.
Honestly you have like tons of team set up to make, it's just the best if we use them based on the situations such as the enemy/bosses gimmicks or etc.
There's more and tons set up available, i had just listed a few of it.

1: There's fights where the order of your party is getting changed from what you choose thanks to a quake...is annyoying and cant be prevented.

2:There's one enemy who takes 0 damage from good alignmet servants, and half-dmg from aligments who are evil or neutral...so, only Herc (Chaos Insane), Zerklot (Lawful Insane), Nero Bride (Chaos Bride) and maybe Tamamo Lancer (Neutral Summer) will cause normal dmg to his 300K+ HP. And is a Rider...grab a friend Herc with Bond 10 CE, combine with your Zerclot and Waver, see how far you can get.

3: Remember Mordred, spamming her NP?

You have 1 fight with multiple zercs who, each one, do that (at least they are ST).

So, you wish for at least 2 powerful AOEs to get rid of them, plus a Taunter or two, to bait them when all goes wrong.

Here's an idea: Raiko (initial NP CE), Zerclot (same), Waver, Mash in the 4th spot, Georgious in the 6th. Chaldea Combat Suit.

Charge your Zercs NPs with Waver, move him to the bottom to bring Georgius.
Activate Gutts+ Taunt with Georgius, get one Zerc to do the AOE attack. If some are alive, they will attack Georgius.
Rise and repeat with the other Zerc for the next Wave (who has the same things), Mashu will take Georgius place once he dies, giving you up to 4 turns free to crush your enemies with AOE NP/crits generated from their NPs.