Plugin Help Item drop help

Hello Bukkit forums, I need some assistance. I am making a plugin Called RareDrops which allows the player to have a rare chance of an extra item dropping, the problem is that I have tried chance systems and weighted Arraylists, I have not succeeded in doing those two because the rate is either too frequent or too rare. Here are my items:
Legendary Helmet
Legendary Chestplate
Legendary Leggings
Legendary Boots
Rare Helmet
Rare Chestplate
Rare Leggings
Rare Boots
Normal Helmet
Normal Chestplate
Normal Leggings
Normal Boots

Thank you.

Oh and I forgot to add
out of 100 kills
Legendary: 0.1% - 0.4%
Rare: 1%-4%
Normal: 13%

bump

EDIT by Moderator: merged posts, please use the edit button instead of double posting.