@ks3v3n

Opening w/ B3 for a free Thunder/Halfcast F3 for the additional Fire in the opening rotation results in a higher DPS after the beginning of the first rotation.

B3: 220 Potency(176 under AF3), 3.5 sec/cast
F3: 220 Potency(176 under AF3), 3.5 sec/cast
T2: 50 Potency, 2.75 sec/cast
F1: 150 Potency(270 under AF3), 2.5 sec/cast

B3>T2>F3 is 8 Seconds, 446 Potency; 55.75pps(from now on referred to as "Rotation 1")
T2>F3>F1 is 8.75 seconds, 540 Potency; 61.71pps(from now on referred to as "Rotation 2")

So obviously, Rotation 2 seems like it's higher

Lets do a full rotation

Rotation 1 allows for 5 F1. An additional 1350 potency over 12.5 seconds. (1350+446)/20.25 = 88.69pps

Rotation 2 only gets 4 F1, and already used 1 in the opening. So it ends its first rotation w/ 3 additional F1 and an additional 7.5 seconds
(540+810)/16.25 = 83.07

As you can see, Rotation 1(opening with B3) is clearly more PPS over a full rotation, simply do to the additional F1.(Not even taking into account the chance for an additional Firestarter)

Now, the difference between them is 5PPS, by no means a large amount, and probably not a very large determining factor of your overall DPS in a fight.

However the fact is using Rotation 1 will have resulted in more damage over a full beginning rotation than Rotation 2. You could try to argue that R2 has a quicker chance to proc a Firestarter, however it needs 2 Firestarter before it will be doing more damage, and you only get 4 chances, compared to 5 chances with R1.