I’d like to suggest a small change to this item which makes it more flavourful, just like Leoric’s Crown which amplifies a gem by increases its effect, i think Leoric’s Signet should have a legendary property that amplify a gem by saying:
“Socketed gems gain all 3 effects. This effect does not apply to Legendary gems”
This replaces the xp bonus which can be gained by socketing a red gem.