BLM: A mini-guide for effective DPS

[-Snow]

[B]
Thunder vs Thunder II vs Thunder III, hardcasting during UI3

(DoT potency * Ticks) + Initial potency / cast time = DPS
Thunder -- (35*6) + 30 / 2.5 = 96 DPS
Thunder II -- (35*7) + 50 / 3 = 98.3 DPS
Thunder III -- (35*8) + 60 / 3.5 = 97.1 DPS

The calculations seem to also concur with the widely regarded opinion that hardcasting T2 is better than T3 during UI3, but the difference is so small, which makes it negligible.
However, the main factor to consider for the choice of Thunder is the DoT's duration. DoT clipping is a DPS loss, as reapplying a DoT does not add on to the current duration, but instead overlaps it with a new DoT, and any remaining ticks of Thunder DoT remaining before it is clipped basically equates to a DPS loss.
Thus, Thunder could be more ideal than Thunder III as it reduces the chances of clipping the DoT, moreso if you get a Thundercloud proc while the DoT is still on the target.

You are not mentioning the Thundercloud Proc potency, which would be the main reason using Thunder III. With Thunder I you will loose 100 potency. That could need some testing/math.

Thunder III
Additional Effect: 5% chance after each tick that potency of next Thunder, Thunder II, or Thunder III will be 340, have no cast time, and cost no MP

Thunder II
Additional Effect: 5% chance after each tick that potency of next Thunder, Thunder II, or Thunder III will be 295, have no cast time, and cost no MP

Thunder I
Additional Effect: 5% chance after each tick that potency of next Thunder, Thunder II, or Thunder III will be 240, have no cast time, and cost no MP

[B]
Holding of Thundercloud procs for UI3 > AF3 transition

More often than not, when you get a Thundercloud proc during AF3, your Thunder DoT from your previous hardcast would still be remaining on the target. As mentioned above, DoT clipping is a DPS loss.
An alternative solution is to hold the Thundercloud proc until you transition into UI3, effectively using it to replace the Thunder hardcast that you would be otherwise doing.
Although having a Thundercloud proc overwrite a previous proc without using it is also a DPS loss, but with only a 5% proc chance, the chances of this scenario happening would be pretty low.
However, it is also dependant on whether the 12 second buff would be able to last until you transition into UI3.
If you're not comfortable with doing this, then it'll probably be better for you to use Thundercloud procs as and when they proc. Or else, I believe this methodology provides at least some DPS increase as it reduces DoT clipping.

Something you should also think about, DoTs/HoTs are not working the same way as in every other MMO.

You could even get a little DPS BOOST with DoT Clipping, but that's more luck based.

Source: http://www.youtube.com/watch?v=aQGGTKgL8-g