@Totema the spell itself doesn't say cumulative..The spell scroll itself stats Successive use enhances spell potency. Which would be exactly what you said. 2nd cast in a row (successive) is stronger..it works fine. I'm guessing AF3+2 pushes that string to 3.
It's not a cumulative effect. It seems that every second casting of this spell is more powerful, while the rest are just as powerful as the first casting.
the question i want to ask is, is it succesive use of your casts, or can another blm get the potency casting after you? might be an exceptionally good mana burn tool if another blm can get the potency boost after your cast, especially since its an aoe, and probably gets great damage boosts from single targeting, on top of maybe this will open aoe burns if its really good. also, 200k for an npc 160k item.... dumb blms are dumb