Potentials losing rank?

Of course, everyone knows that if an equip is of a certain rank, it won't downgrade in rank. But that's just because the first line is that rank.
Let's say an equip is 6% LUK 6% LUK though. Can the second line be downgraded in rank while retaining the epic status of the first line?

Are you sure you're not confusing Inner Ability and Potential?

you have the wrong idea about potential ranks

there are 4 potential ranks (rare, epic, unique, legendary) but 5 tiers of potential lines which we'll just call tiers 1 through 5. On top of this lines also depends on item level but that's not directly relevant to your question.

each rank draws from two tiers of lines (1 and 2 for rare, 2 and 3 for epic, 3 and 4 for unique, 4 and 5 for legendary) which is why you see 3% and 6% for epic, 6% and 9% for unique, 9% and 12% for legendary. The first line has a higher chance than second and third lines of drawing from the upper tier (i.e you're more likely to get 12% than 9% on the first line). To answer your question, the tier from which each line is drawn can change with every cube so an epic 6% luk 6% luk can be for example 3% str 3% dex on the next roll (if it stays epic).

this is also why you never see flat bonuses (ATT +12, STR +12) on main potential for epic or higher equips because the flat bonus is a tier 1 line which is exclusive to rare potential. bonus potential works in I believe the same way but it has different potential pools so you can see flat bonuses on high potential rank gear because there are higher tier versions of that line.

might be wrong in a couple areas but this is how I understand potential works

only the top line upgrades in rank

the bottom two draw from the potential pool beneath them with a chance of upgrading in tier, but that upgrade isn't saved from cube to cube

So

Legendary/Unique/Unique
Unique/Epic/Epic
Epic/Rare/Rare
Rare/Rare/Rare


When you see something with multiple lines from the same pool, what that means is on that cube, those lines upgraded to that tier, there's a higher chance on tier upgrades on secondary lines, but not primary lines, and of course, tier isn't saved on secondary lines.

It's why seeing a triple max stat is so hard, because not only do you have to win the tier lottery on that cube twice, but you also need to roll that exact line.

only the top line upgrades in rank.

the top line isn't guaranteed to be the highest quality
here you can see my helm which has rolled low in all 3 lines (http://i.imgur.com/YtLtj3b.png)

the top line isn't guaranteed to be the highest quality
here you can see my helm which has rolled low in all 3 lines (http://i.imgur.com/YtLtj3b.png)

Did you cube that with purple cubes?

jesus the potential system sucks even harder than I thought. this pomegranate is anti-consumer.
can't believe you big spenders allow yourselves to get cucked this hard.

I believe Black Cubes and Red Cubes doesn't guarantee the highest quality of the rank.

I believe Black Cubes and Red Cubes doesn't guarantee the highest quality of the rank.

the top line isn't guaranteed to be the highest quality
here you can see my helm which has rolled low in all 3 lines (http://i.imgur.com/YtLtj3b.png)

9% exists within the legendary tier rewards because nexon loves cucking people