I think a low diff is a crazy take if I'm being honest
A number of skirmishes/clashes/fights began and ended over the course of Zoro vs Lucci. This isn't like Zoro vs Apoo where Apoo's goal was to run away instead of standing his ground and fighting
Lucci and Zoro were
actively going at it for a pretty long time with Zoro utilizing various tools in his arsenal to put him down. He even whipped out the green smoke for him at one point
It doesn't make sense to call it a low diff if you're exerting this level of effort against an opponent
If this is considered a low diff then you'd have to give me examples of low, mid, high, and extreme diff fights in One Piece
Cause based on my personal criteria it would be
at least a mid diff