Updated luck info as of 12-10-17.
I bought a second account to just experiment with its characters. Have one now with maxed out luck, totally seems to be a waste of valuable points. I actually only used dexterity, hammer maxed, and luck. I get no different results as whats already posted by boundmore and same results when hunting with others like Cookviper and his nephew.
At the end of it all, “yay” you get more of the most abundant coal in the game, and no more gems than your partner while hunting after 4 hours. So to me it’s not worth it. I’m not even sure if its worth a single point. Maybe max out Attributes Bonus, which gives you equivalent to 1 point in all skills, more bang for the buck. Get your luck that way.