I think the optimal Cthun decks don't need to run all the shitty Cthun buffing minions. Just enough to get value our of Cthun. People will soon realise a 2-mana 2/3 that does nothing is a really bad play.
I can't see what else I might run. Flame juggler is the only thing I can think of atm, which is a bit better against aggro admittedly.
What I am doing is working though. There has been a single time I haven't had 10 attack by turn 7 for twins. And that time I played the sole twin, I won the game because I wasn't holding out for maximum value, but merely stalling to get an equality clear.
I run the 2x 2 drops, 1 twilight elder (w/e the 3/4 is called for 3cc), 2 disciples of cthun, and the 4/2 divine shield.
That's it. I don't run any of the big minions because I think those are the ones that seem bad compared to other minions of the same cost. And brann bronzebeard occasionally acts like an additional activator.
I have thought about running doomcaller though.
Main question is if you can reliably enough get to 10 attack before you want to play all those minions that only get buffed by a 10 attack C'thun.
Might be hard without the generic 2 mana 2-3 and 3 mana 3-4.
Twilight elder is pretty meh. I had no issue cutting down to 1 of them and I only kept 1 because it removes a feral spirit and survives. Occassionally it buffs your cthun a ton too.
Disciple of c'thun and the 4 mana 4/2 divine shield are the two all stars. But I agree that you probably need the 2/3 to consistently hit 10 attack.