Should I level Blue Mage?

[HappyHaunt]

I say if you have spare time or are bored go for it.
Just know there is not much to do that has not already been done once you hit 50.
Masked carnivale is good for seals like you have said

I was actually a bit confused when I heard they had released a 'limited job', I guessed not many people would even bother with it.

[Burningskull]

You can level it. But good luck getting all your spells now that the "newness" has worn off and hardly anyone farms spells.