Just some observations, corrections on some things you've said

1. Single Target:
You're missing out on an additional Fire1 and potentially another Firestarter Fire III - Huge dps decrease over the course of a 5-10 minute fight.

If your MP is above 700, cast another Fire 1, then swift cast flare to use the remaining MP. If convert is up, use it and then cast another Fire 1 followed by Blizard III -> ThunderII or Scathe.
You need minimum 250sh MP to cast flare. That's great DMG potential and MP efficiency when combined with swiftcast.




you can either start with a swiftcast ThunderIII if its a boss with a large enough HP pool to justify using your swiftcast, or incorporate Swiftcast-> Flare


2. AOE
You can transpose and then spam BlizardII as you climb the MP refresh.

Another side note, BlizardIII is not poor DMG by any means. Its inferior to FireIII and Fire1 spam in Astral Fire mode, but it isn't weak by any means. My BlizardIII's can crit for more than 1k.