Should Thunder be left out of rotation for BLM?

[Acidblood]

Rule of thumb: Yes, Thunder is worth using.

Details for single target:
- A rotation with 100% Thunder DoT uptime + 1 appropriately timed Thundercloud proc is better than a rotation without Thunder.
- A rotation with 100% Thunder DoT uptime + 2 appropriately timed Thundercloud procs is much better than a rotation without Thunder.
However:
- Spamming Thundercloud and thus overriding a significant duration of the DoT is generally not worth it as the direct potency per second of Thundercloud is less than that of the overall rotation (i.e. a DPS loss)
- A rotation where you are always hard casting Thunder is not worth it, you want at least 1 appropriately timed Thundercloud proc in there (which can be forced with Sharpcast) to avoid cast time / MP issues / potency loss.

For AoE:
- AoE Thundercloud is always good, so keep the DoT up and force procs with Sharpcast... Instant cast AF3 Flare and Foul are better though, so just spamming Thundercloud isn't necessarily a good idea, especially since good timing will help you keep the DoT up and (hopefully) avoid having to hard cast Thunder.

No, why would you ignore it :O
Your thunder dot uptime should be as high as possible. Since astral fire lasts longer now, you are even safe to hardcast thunder in your fire phase (if the dot ran out) without loosing astral fire. And the thunder proc is nice for movement too.

No, No and NO! If Thunder falls off during your AF phase, and you don't have Thundercloud, just let it go and get though the rest of your rotation faster. Hard casting Thunder isn’t worth it, especially if you end up screwing yourself on MP and losing a F4 / Despair.
Note: Hard casting Thunder in UI is different as you are generally waiting on MP anyway and will (hopefully) get or force and Thundercloud proc for use in AF.

[supaiku]

No, No and NO! If Thunder falls off during your AF phase, and you don't have Thundercloud, just let it go and get though the rest of your rotation faster. Hard casting Thunder isn’t worth it, especially if you end up screwing yourself on MP and losing a F4 / Despair.
Note: Hard casting Thunder in UI is different as you are generally waiting on MP anyway and will (hopefully) get or force and Thundercloud proc for use in AF.

If you start your Astral Fire phase with the full 10.000 mp the thunder cast won't make you loose a F4 or Despair. That being said, you are right, normally one should have the Thunder proc for AF anyway, at least I think I have the proc during my fire phase like 95% of the time.