[1.2.397] Demon Slayer (3)

umm...
tell me, when was the last time you got "Feel angry for 10 seconds" on a unique helmet?
Oh, that's right.
Never.
Because the data for potential makes it so that you can only get the potential lines that are listed at that tier. You can't get things like happy for a certain amount of time on a unique equip, because that's only for rare.
Same applies in this situation.

If it's the same as the current system as far as lines go;
All *rank* items would have *previous rank* primary lines as secondary line.
All 'legendary' items should have secondary lines of current unique primary lines.
Your example is a sh'itty one, cause 10% chance *face* is a rare primary line iirc, so it'd only be on rare items as primary, and epic items as secondary.