According to Yoshi-P BLU are too powerful a job to be a real playable one in normal content, and I have to say that's pretty true, seeing how the presence of an BLU breaks up dungeon mob packs by itself into 1 or 2 spells.

As mentioned above, an Ishgardian is an Elezen living in the polar north.
To say that an Ishgardian is not Elezen is like saying that an Eskimo is not a human.