There was already a forced ice cast in UI pre level 58 because you needed to fill around two GCDs' worth of time while your MP regenerated and even a thundercloud proc, which you might or might not have, would only consume one of them, and without a proc you might already have enough DoT remaining on an enemy that refreshing it is pointless. On a bad cycle you might find yourself either casting back-to-back Blizzard 1s or casting a single Blizzard and then just sitting and waiting for another second or two.