Fire II isn't bad at all.

Transpose -> Flare -> Fire II -> Flare is actually slightly higher DPS than without the Fire II. I typically include it unless going straight to the second Flare will kill for sure.

Fire III -> Fire II -> Fire II -> Fire II -> Flare is higher DPS than the above, but it requires more downtime to do repeatedly; by the time you have the MP to do it again, the DPS is reduced below the Flare only rotation. You would want to open with this, use up Convert/Mega Ether Flares, then begin the Transpose -> Flare -> Flare rotation if stuff is somehow still alive.

Starting off with Fire III -> Flare seems like it's a good idea because it is higher DPS than including the Fire IIs, but it's for such a short period that the actual result is less damage dealt.

Some numbers:
http://forum.square-enix.com/ffxiv/t...=1#post1817257