Scathe

[Taranok]

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).

You could maybe increase the potency to 150 (with a 20% chance of 200 still for an 'effective' potency of 160), or alternatively increase the chance of doubling to 50% or 60%.
That, along with a 3s refresh of AF/UI, would make it functional without disrupting the BLM rotation.

Considering at level 90, fire 1 is literally being removed from the core rotation, not sure it matters that Scathe would do more damage at that point. Especially since you're usually swapping out a Fire 4 at 540 potency for a scathe, not a fire 1. Also as brought up, fire 1 is still more potency anyways.

Remember, that's the important thing scathe does. It doesn't stop you from casting a fire 1, it stops you from casting a fire 4. And at 90, fire 1 isn't used. You'll still get that paradox off, but the fire 4 is what's dropped from the rotation. Hence even at 300 potency, it's still a 240 potency hit. This is, of course, ignoring maim & mend and enochian's buffs, but it's still relative.

For comparison, Summoner, currently, drops about 40 potency. Scholar drops 90. WHM drops 180 (if they resort to Dia spam for movement). RDM is...I don't actually know, but think it's in the 1-200 range where, currently, the first 3 in any given 2m cycle are 'free' due to manafication timers.

Currently, BLM loses 440 potency for casting scathe. And most of the meme strats revolve around not casting fire 1 specifically because its DPS scales so abysmally. That's probably the entire reason the devs finally made fire 1 worth casting in the AF phase in EW, because they got tired of the meme rotations.