Luffy and Zoro are high up there, but the do still have endurance issues.

I really think there will be a "control your Haki better" training arc.
I think that'll be Elbaf, though it could happen in Hachinosu too.
This isn't a hot take or anything but Shiryu will probably push Zoro to awaken FS to sense him and beat him, which will finally put his CoO near Mihawk's level.