I like to calculate luck's effects a different way, by the way.
Anyone who likes it, feel free to use. Credits appreciated but not neeeded.
((a.luk - b.luk)/(a.luk + b.luk))+1
that would make:
an attacker with 999 and a defender with 1 return ((999-1)/(999+1))+1 = ((998/1000))+1 = (0.998)+1 = 1.998, about 2
an attacker with 1 and a defender with 999 return ((1-999)/(1+999))+1 = ((-998/1000))+1 = (-0.998)+1 = 0.002 almost, but not really, 0.
of course, there are the two extremes. in a real game it would be much closer to
an attacker with 15 and a defender with 10 return ((15-10)/(15+10))+1 = ((5/25))+1 = (0.2)+1 = 1.2, and inverting them we get ((10-15)/(10+15))+1 = (-5/25)+1 = -0.2+1 = 0.8. Same results with 30 and 20 if you do the math.
As you can see, it escalates much better with the difference in luck between the fighters. The one with higher luk still has an advantage, but it is much more noticeable. A bigger difference gives a bigger advantage, but the scale of the difference is the important part, not the numbers themselves.