Actually, now I think about it having a 99% chance for a critical might be a tad OP, so what about this: each hit, the game makes N 'rolls' (like throwing a dice), where there's a 1% chance of a critical, otherwise it'll be a normal hit. N is simply the number of points you have in luck. For example, with 10 luck you would have a 100*(1-0.99^10)=9.56% chance for a critical, a 39.50% chance at 50 luck and a 63.02% at 99 luck.

Which of these critical hit systems do you think is better (if any)?