I thought Blizzard was pretty nice when the cooldown was made to be slightly shorter than the actual duration of the effect. Now that we have the target-centered vs. placed versions, it seems the cooldown is exactly as long as the duration. In practice, there’s usually a slight gap between two blizzards and it just makes it feel clunky.
Suggestion: shorten the cooldowns slightly and consider making the placed version have a tiny bit shorter cooldown or at least allow using the reticle (but not clicking on it) just before the cooldown ends.
They could even implement it so that the spell would say that you can only have one Blizzard up at any time and that the new one would replace the old. This would be fantastic utility in situations where the targets move significantly from where you expected them to be. (And there’s still a penalty for “missing the mark”, because you are using a global cooldown to start the new one ahead of time.)