It's not about the +eggs, it's the orb changers and heart breakers in particular. Having orb changers isn't just about giving you enough colors to activate Kirin, it also can tremendously boost your damage.
Basically you can think of it like a multiplier, since every orb you consume increases damage. If you pull off a regular Kirin burst vs a Kirin burst with Valk + Verche the damage difference is huge, like way better than King Slimes or any of those guys huge.
Like here's some numbers:
Lets say you have a 5k light attack Kirin team and you do a basic x25 match with 3 orbs of each of the 4 necessary colors. The Damage calculator says that would deal 218750 light damage.
Lets say you have some sort of x3 light active skill in there. That's 656250 damage.
Now on the other hand if you run orb changers instead of a x3 active skill. Let's say you have a valk and a verche and each provides just 4 extra light orbs which you match separately. That's 1093750 damage! Much more than the x3 active gives.
Even if you match all of those light orbs in a big cluster and miss out on damage from having more combos, that's still 656250 damage. Yep having just 8 more light orbs gives as much damage as a x3 active.
Of course it's possible to have more or less than this depending on your board, but if you can properly manage your orbs the damage potential is huge.
My point is you don't need stuff like Sandalphon or Takemina or whatever to deal good damage because Orb changers make the biggest initial difference.
Of course to hit the next level of damage you then stack multiplers on top of orb changers, but you can never neglect orb changers because that's where most of the damage comes from.
This goes for Bastet too. You can get a lot more damage if you build mono green with rainbow subtypes and have Chu somewhere in there. And then if you have a slime burst on top of that you're golden.
Oh yeah on another note though base stats do matter a LOT. If you don't have plus eggs then at least you want to farm Super Dragons until everyone is level 99 before you try tackling descends.
