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What others have said ^. Especially about the AoE = cranky mobs comin' for ya in the dungeons (which usually leads to cranky tanks :p).
But I'm going to add in that I usually go Thunder II > Aero > Blizzard > Fire III > Fire (til out of mana) > Transpose etc. I like putting Blizzard in there for the Heavy effect. (I'm usually synced down in dungeons thus far and haven't had opportunity to make use of Blizzard III yet.)
Here is my rotation for my level 36 BLM. Thunder 2 > Swiftcast > fire 3 > fire 1 (until out of mana) > transpose > thunder 1 > blizzard 1 > fire 3.
Once I get blizzard 3 I will eliminate transpose from my rotation and make sure I conserve enough mana after casting fire to cast blizzard 3. I use swiftcast before fire 3 everytime it cycles to maximize my dps. If thundercloud procs I often pull hate off the tank of he is undergeared or not consistently doing his rotation.
Aero or bio do little damage compared to my class skills so I don't put them on my hotbar.