My Conjurer just got to level 46 this weekend, and I was rewarded with the shiny new Aero 2 to replace the tired old Aero 1 that I've been spamming at mobs since level 4. Just looking at the tooltip, Aero 1 does 50 potency instantly plus 25 potency every 3 seconds for 18 seconds (200 total potency) and Aero 2 50 + 40 * (12/3) = 210 total potency. I'm not greatly impressed by the 5% improvement in power given the (108-86)/86 = 26% increase in mana cost. I suppose the benefit of the spell is that the damage is front-loaded relative to Aero 1, since it has 2/3 of the duration.
Then I remember that dot mechanics are a bit broken in FFXIV, and that with very high probability a dot loses one tick at the end of its duration (source). So the total potency calculation is really more like 50 + 25 * (18/3 - 1) = 175 for Aero 1 and 50 + 40 * (12/3 - 1) = 170 for Aero 2. Paying 26% more mana typically incurs a loss of 5 potency in damage. Aero 2 is therefore not on my bars.
Am I missing something, or does this spell really have no use in the game as it exists today?