Only Paul knows, we others guess by testing without gaining true results.
One thing for certain, Magic Luck gives you a % chance for an item to become an Overspawn item. What this means is the max stat/mod on a certain tier item can go up by one(1) tier.
Tier III has a maximum of +15 to Stats (Str/Dex/Vita/Int) and if it becomes an Overspawn (only if you are wearing Magic Luck items), the the maximum will become +20 to Stats (Str/Dex/Vita/Int), so it could be Tier III +16, or 17, or 18 to maximum 20. And yes, you can get two(2) overspawn modifiers on 1 item ... could be Tier III Club +17 Str & +16 Vit.
Still RNG wins outright.
Oh, better to Mute items with ML on I believe, but then you have to get good ranks also.