Originally Posted by
Majad
Honestly, I think it's only worth it on uniques like rings and necks that might be cheap, like 10 exalts or something. I mean, as long as you can afford to buy it again, you can risk it, but I think it's more fine to risk it on cheap uniques since their mods will always be the same if they won't change into a rare.
Edit: Actually, rings, neck and quivers are probably the 'safest' items to use a vaal orb on because they don't have any sockets, regardless of being an unique or not, so the penalty should probably be lower.