That the characters in universe know of. Its just never happened before. Coudl also make an argument for the player character somehow staving off the full transformation. None of this will happen in game anyway, I'm just sayin'. ;)
Printable View
It was spelled out in the lore at the release of Aht Urhgan, IIRC. <.<
If not, the BLU AF quests make it quite clear.
Besides, Soulflayers are Black Mages. Do you really want your two-hour to turn you into a Black Mage?
"Oh whoopee, once every two hours I can cast Burst II instead of 1000 Needles" <.<
Much more interesting to see what happens when you throw aside the spell slotting restrictions for a minute and get a BLU with a bajillion job traits and stat bonuses (plus many more spells to choose from for casting.)
===========
ON that note, these are the stats you get from slotting EVERY blue magic spell:
HP+80
MP+188
STR+27
DEX+32
VIT+35
AGI+43
INT+19
MND+32
CHR+7
If you bump off the negative modifiers (this is a two-hour after all,) then add these:
HP+115 = HP+195
MP+10 = MP+198
STR+3 = STR+30
DEX+1 = DEX+33
VIT+1 = VIT+36
AGI+1 = AGI+44
INT+4 = INT+23
MND+4 = MND+36
CHR+14 = CHR+21
THat's on top of twenty-eight different Job Traits ( http://ffxi.gamerescape.com/wiki/Blue_Mage/Job_Traits ).