I made a lot of calcs recently because I recently started posting FCoB BLM specific guildes and I am one of those who open with Blizzard 3. I got really interesting that from this: Video link
Spreadsheet: Aikaal's Spreadsheet.
If you don't wish to see the video and just get the short details, here's what I got:
Cons with B3:
- Requires a minimum of 22 Piety or higher from your base race stats. If you have 21 Piety you must spec an extra Piety somewhere.
- Requires Scholar in the party.
- Have about 5% chance or not getting the 79 mana tick to be at 3465 mana (I play a dunefolk Lalafell)
Pros for B3:
- Total of 6 Fire casts in your opener while you have voiced foe, raging strikes, potion, trick attack. This is the most important and main reason why I use this opener.
- Longer burst.
- higher chance of procs.
Cons of T2:
- Doesn't utilize raid party buff and it's best.
- Relies on awful rng luck to get an extra proc.
Pros of T2:
- Any race can use it (I understand some people dislike Moon Miqo'tes or Dunefolk Lalas)
- Really good to use if early Flare is requires or double Flares like in T12.
To resume, the only time you will get all the buffs from your raid at the same time. B3 maximizes it without hoping for a lot of procs. It makes your burst longer.
The only and only difference between both of opener is B3 is behind T2 rotation by 1 GCD. This is why in PPS when T2 just cast his B3, this rotation ahead. Because they both have 5 Fire 1 cast at this time. Due to procs and rng, two black mages are bound to have better / worst rng. In the end, it does not matter.
The only thing and the most important thing to learn from what I did is that a 6th Fire will always be beneficial when your bard sings, your ninja trick attack and you have raging strikes and pot.
In a situation after Teraflare for example. I have nothing up and if my bard doesn't have Foe, there's no reason to delay my Fire rotation and I'd open with T1. Hell, I'd probably open with F3 and T1 isn't even great.