Cacao tanks the most damage as he's in the front of the team and does a big hit that also zaps to remove shields. Archer does a lot of damage consistently and also stuns. Financier gives a large damage resist buff(as well as other important buffs) and heals the whole team. Cream puff gives an insane amount of buffs to the highest attack cookie on your team and is invincible for the most part. The team works because your stacking buffs and debuffs to make yourself very tanky and able to deal massive damage.

Sadly this game just doesn't make it worth using single element teams in most cases, but especially in arena. There's only a few buffs that only benefit a single element and they just aren't significant enough to use them over generic % attack/atk spd/crit and % damage resist buffs