1 luck would be ok in a pure damage build(in example jeo the rock). He will do almost no criticals anyway.
Haymaker adds 15% to critical.
So with 1 LK it'll be 16% critical.
But if you have 6 LK and some more crits, you may have almost every non-aimed punch critical.
Max possible without finesse is 25%+15%=40% in torso.
But with new Stonewall perk, knockdowns are... useless, because he'll have 10 EN and will be immune to knock downs, while critical non-aimed punch without knock downs is simply.. useless, yeah damage... but you'll deal more with SMG burst, and you get them anywhere, making non-aimed HtH build useless.
So better use aimed HtH build and aim in the eyes.
And even better don't use HtH build, but BG/SG-burster build. Right now they playing role of tanks and "melee".