Someone said that none of the SH were surprised with G4. Probably because they knew about it.
I am 100% with you. Zoro knew for sure Luffy could defeat DD but unfortunately Luffy can't really tell how strong is opponents really are.
He wasted more than half of the fight using g2/g3 and wasting haki. Had he used G4 from the beginning, after red hawk or after gamma knife could have changed the events of dressrosa and avoided the 10 min of rest.
Zoro said to hajruden to sleep that when he was to wake up the bird cage would be gone but he was wrong for relying in luffy.
If there was no Sabo and gladiators burgess or DD would have had their way with Luffy.
How many more times will zoro have to tell Luffy to get serious?
Luffy will always be like that. But once he gets serious it's great. Like hopefully now with kataguri