The revealed potential thread!

Not sure if this was a good move. With the before potential I would be at 410% boss and 146 pdr.
The after potential would have been 345% Boss and 206% pdr. Did I make a mistake? That 12% luk really annoyed me though.
I'm really struggling with this weapon...

It's a decent potential for C.Vellum (although I find %Ignore on equipment to be unnecessary seeing how 1) Xenon can achieve ~90% multiplicative %Ignore with just skills/links and 2) it's possible to stack up on %Ignore from party skills), but not as an effective potential for other bosses (although it wouldn't really matter since you'd be able to kill them anyway).

 Side note

I think you may have been fed the misconception by your peers that having a large amount of %Boss/%Total whatever is a "bad thing" and therefore it's best to recube your weapon potentials for %ATT, because it's not necessarily true and I believe this sort of thinking can be misleading. It's just that an additional x% Boss (when you have a large amount to begin with) will yield a smaller, diminishing %increase relative to an additional y% ATT (something that you're most likely lacking). The idea is to maintain

 a balance

where the two "+new" potential lines at legendary (e.g. +40% Boss vs. +9% ATT) will produce two ratios that are roughly equal to one another.

If you feel that the former is too high, then the remedy is to get a fix from bonus potential for the latter. Not cutting back on the former in exchange for the latter. So if I were in your position, I would have just left the "before" potential as it was, and waited to cube the bonus potentials for %ATT.

 Some stuff

It's likely +70% Boss will begin to approach an equivalence to +21% ATT (which you may have been previously aiming for). Because those two potentials are literally the same thing, the only way to get something "better", is to land on something relevant for the third potential line (e.g. %Ignore, %ATT, %Stat). At this point, I think it's a waste of funds to aim for that third line, unless you stumble upon it on incident.

 More stuff

+%Boss/%Total and +%ATT increases are uniformly effective against all mobs, which have different %PDR's. If you want to cross-examine how %Ignore (which has a pseudo-exponentially growing property of effectiveness as you go up the %PDR scale for mobs) compares to %Boss/%ATT combinations, then some math is required. But for the most part, you can use your intuition and conclude that a %Ignore combination will be most effective at C.Vellum.

That was really helpful! Thanks again! I still have the after potential on my whip blade though, so I'll just wait for bonus cubes and miracle time again
Currently 1% Atk is equal 4.6 %boss. I included the Demon Avenger and Kanna link skills into the calculations. (Not sure if it counts towards total damage though)

Yeah, they do count as total damage. And if you want to be more precise, the Reinforce Hyper (+20% Damage to Mecha Purge) also counts toward the %Boss/%Total sum, but that number you calculated already gives you a good indication of how things are.