Scathe

[Rongway]

I don't think Scathe should be more potency than Fire I, especially if it has the effect of extending AF/UI.
Fire I is 180 potency, while Scathe has an 'effective' potency of 120 (100 +20% of 200).

Fire I's potency under Astral Fire III is 324.
Fire IV is 540.