One of my takes on it for years has been that we saw Shanks use it in a huge range on Whitebeard's ship to the point where people were dropping left and right, and even the ship was getting damaged, but what if the user can concentrate it to less of a range, and it becomes even more potent. We know that in quick blasts, it can remove fodders instantly, but if you have the Willpower to withstand it, you won't pass out, but you do start sweating, so we know it does have some kind of effect on people regardless. It might be something like, even though you can withstand passing out, the longer you're subjected to continuous CoC, the weaker you start to become. You're essentially trying to remain conscious while fighting, because you're constantly being bombarded with CoC.
Normal coc acts instantaneously(It anesthetizes everyone in an instant) .....But Shanks uses coc for a few seconds