Foe Requiem

I saw some questions about this, and very few answers.

This is the wiki's take.

Not very informative, is it?

Let me begin by asserting that I have no concrete numbers to back up my assumptions -- but I can compare with other tiered songs. For example -- singing Army's Paeon V produces a 5-tick regen effect. Singing it with a +2 Paeon instrument produces a 7-tick regen. I assume that Foe Requiem's damage is calculated in a similar fashion. Thus:

FR I = -1 (-3)
FR II = -2 (-4)
...
FR VI = -6 (-8)
*Numbers in parentheses represent the effect of using a +2 Instrument.

It's reasonable to assume that Requiem works in this fashion. I am fairly confident that Soul Voice doubles the effect of Requiem (it is particularly useful to halt the regen of unclaimed Poroggo Madames, does a fair bit of damage to Salvage chariot bosses, and has applications in Limbus/Nyzul Isle with an active Korin Obi).

Application
Assume that landing Requiem is a lot like landing Elegy. Use an HQ staff if you have it -- they're the best gear money can buy for resists -- and use a combination of Skill, M.Acc, and CHR where available. The effect of Skill tends to be more noticeable than the effect of CHR, and I don't have enough M.Acc to comment. With the +32 of merits, I can reliably land Requiem on targets that are neither light resistant nor immune*. If you have trouble landing Requiem, try putting on more Skill or M.Acc gear.

BRD has no natural enfeebling skill, so it's safe to assume that Enfeebling Magic Skill has nothing to do with songs. M.Attk is known to affect BLM nukes, but there's no evidence that ties it to the effectiveness of an enfeebling song like Requiem.

Bard song effects tend to be constant, anyway -- with the notable exception of Etudes, whose effects decay over time.

---
*My stick rate on Poroggo Madames tends to suffer if I haven't unlocked my Apollo's Staff, for example.

---

Additional Reading:
Discussion on BG