Here's a question.
... which you might actually already have a calculator for, but I'm lazy!
Not that we've learned of Vine, how important is Cthulhu for Water teams?

My Mordred-Belphegor-Triton-Ryu-Oh-Sol team is doing very well. But, what irks me the most is Sol's damage output. Against neutral, the other team members whack for ~25k and Sol for ~7k. Swapping Sol for SSR Nike should increase minimum damage output per turn from 107k to 125k.

Of course, there are a whole load of ups and downs.
+ Using Cthulhu gives access to Overdrive Extension. Not something I've played around with, but I'm sure it's ridiculously powerful, particularly against tough match-ups *cough*Thunder wave2*cough*
+ Cthulhu, if replacing Belphegor, would get me a third -Atk A debuff, allowing me to -50% the entire wave1. Not sure if I want to replace Belphegor though, since replacing Triton would mean that I'd be able to 1-turn neutral element wave3 Rage phases (due to Cthulhu having higher Burst modifier).
+ Frees up Vine for more stats from an Eidolon stats.
+ Sol isn't as vulnerable against Thunder.
+ Sol gives instant access to -50% Atk, even in wave1.
-+ Back-up A Def debuff from SSR Nike would be very good, but Cthulhu effectively does the same damn thing. Actually a bit better since it stacks with Ryu-Oh when necessary.
- A 16% damage increase just from having a fifth Water character is no freaking joke.

I have plenty of time before the second Miracle Ticket, but regardless of what happens I don't see dropping Cthulhu entirely. It's just a matter of which order do I get Cthulhu-Water Raphael-SSR Nike.