Apparently I'm distracting (and not the good kind)

[ChaozK]

Or maybe they halved the potency so people would use Fire II???

Doubt it as the same patch that nerfed it also made it available as a cross class skill, so surely they had SMN and SCH in mind when they nerfed it (WHM has Holy). It was made a cross skill as a they removed lightning because it was too op for SMN at the time.

[UBERHAXED]

Doubt it as the same patch that nerfed it also made it available as a cross class skill, so surely they had SMN and SCH in mind when they nerfed it (WHM has Holy). It was made a cross skill as a they removed lightning because it was too op for SMN at the time.

They couldn't make it obvious that Tri-Disaster (as it was named at the time) was useless. But the reason was to fix the AoE imbalance. Of course, it went without saying that the end result didn't quite go as expected (they simultaneously changed timings for UI and AF) and we ended up using a "rotation" that just consisted of Flare (i.e.):
Fire 3 -> (Fire II filler) -> Flare -> Transpose -> (mana tick + 2 seconds) -> Flare -> Flare -> Transpose -> (mana tick + 2 seconds) -> Flare -> Flare -> Transpose -> (mana tick + 2 seconds) -> Flare -> Flare -> Transpose -> ad infinitum...