I was shocked too
I started with Gaella in dps slot since she has 27k total attack with U str card but that ended with 260-280 millions.
But thinking about it it makes sense.
I gave Belle my main character mage staff and offhand so she ended with 17k total attack, I have SS boss card equiped on her so effective attack is in 25k range.
Then she has splash damage on her normal attack so that's solid multiplier to her damage on hydra. Then she has her buffs - normally she only had 50% uptime for them but CDR solves that problem so we get 1,35 modifier to attack of whole team most of the time.
And she also has her summon which adds damage and more importantly with some RNG luck can stack even more buffs.
Raven is similar - no aoe but she also increases attack speed which stacks with CDR and in turn gives more buffs from Priest, Belle and Raven herself.
I don't have proper dps deity outside of DBS but they would need to do really lot dmg to compensate lack of one of multipliers on whole team (altrough in case of DBW he has aoe damage and team buff too).