I agree, nothing implies that Zoro's CoC is Lacking, it's just being Wasted,
Like someone who leaves water valve open, Gaban was like wondering: "Hey why are you wasting all that water?", not saying it's Quality is Poor,
Also, leaving your Haki Active at all times (even if small leak) is taxing on the body, it's like you're in a state of combat at all times, yet Gaban was shocked that Zoro was at ease with it, it's like someone who's walking in double gravity yet doesn't know it,
However, I want to clear another misconception, Zoro did not use Haki against Mr. 1,
Haki doesn't make your sword pass through some Paper without harming it,
It also doesn't make you sense Objects & Environment as if it was Living Beings,
Haki manifests from Willpower, but Haki isn't Willpower, so don't assume any feat of Willpower is a feat of Haki.