In regards to the accuracy of certain additional effects on weaponskills and blue magic, my post from FFXIAH:
My current hypothesis is that it has something to do with the way that certain additional effects resist. Currently I've only documented defense down, blind, and accuracy down additional effects having the problem, and I suspect that these status effects, possibly more, have some issue regarding the specific code bits that govern these additional effect's resist states; i.e. full duration, half resist, full resist. The only wrench in the scheme is Hecatomb Wave, which has no specific duration, however it's possible that even when randomized it can cut the randomized duration in half on a resist.
Currently affected abilities and spells (the ones I've tested):
-Tourbillion (Add. effect: Defense down)
-Sandspin (Add. effect: Accuracy down)
-Barbed Crescent (Add. effect: Accuracy down)
-Hecatomb Wave (Add. effect: Blind)
-Tachi: Ageha (Add. effect: Defense down)
Ones recently tested by others:
-Metatron Torment (Add. effect: Defense down)
-Onslaught (Add. effect: Accuracy down)
-Full Break (Add. effect: Accuracy, Attack, Defense, and Evasion down)
-Armor Break (Add. effect: Defense down)
-Shell Crusher (Add. effect: Defense down)
-Randgrith (Add. effect: Evasion down)
-Nightmare Scythe (Add. effect: Blind)
-Skullbreaker (Add. effect: INT down)
I suspect that similar abilities and spells would behave the same way. I can't test anything else, nor can I file a report on the official forums about the relic weaponskill(s) that are affected, as my subscription lapsed a few weeks ago.
If anyone wants to test some other things, the weaponskills I'd want to look at next would be:
-Gate of Tartarus (Add. effect: Attack down)
-Blade: Metsu (Add. effect: Paralysis)
-Guillotine (Add. effect: Silence)
-Tachi: Yukikaze (Add. effect: Blind)
-Tachi: Gekko (Add. effect: Silence)
-Tachi: Kasha (Add. effect: Paralysis)
-Weapon Break (Add. effect: Attack down)
-Wasp Sting (Add. effect: Poison)
-Viper Bite (Add. effect: Poison)
-Exenterator (Add. effect: Accuracy down)
-Blade: Retsu (Add. effect: Paralysis)
-Shattersoul (Add. effect: Magic Defense down)
-Vidohunir (Add. effect: Magic Defense down)
-Garland of Bliss (Add. effect: Defense down)
-Omniscience (Add. effect: Magic Attack down)
-Seedspray (Add. effect: Defense down)
Abilities and spells that are
not affected:
-Blade: Kamu (Add. effect: Accuracy down)
-Shijin Spiral (Add. effect: Plague)
-Blade: Yu (Add. effect: Poison)
-Shadowstitch (Add. effect: Blind)
-Head Butt (Add. effect: Stun)
-Sudden Lunge (Add. effect: Stun)
-Delta Thrust (Add. effect: Plague)
-Spiral Spin (Add. effect: Accuracy down)
-Benthic Typhoon (Add. effect: Defense and Magic Defense down)
-Bilgestorm (Add. effect: Accuracy, Attack, and Defense down)