Your best bet for this kind of data retrieval will likely be BLM and DRG.
Fire 4 is a total of 504 potency, plus some other % damage buffs, but the effective potency is consistent and very high. It should provide values in the 2000-2500 range, which reduces rounding error to <0.5%.
For autoattacks your best bet is probably DRG, ignoring Heavy Thrust.