Ho I didn't even highlight this when I quote the Live Letter:
Blue Mage is the first "Limited Job" coming to FFXIV. A Limited Job is a job that is meant to be enjoyed in a solo environment and is not suited for parties.

We believe one of the unique traits of the blue mage is the ability to learn and use the monster's abilities that could potentially break the balance of the game. In order to bring out this uniqueness as much as possible, we have made the Blue Mage into a Limited Job that can be enjoyed alone. By Learning, you can enjoy collecting the abilities and also mixing abilities for different situations. The concept behind the blue mage in FFXIV was based on making these three core features possible.
https://forum.square-enix.com/ffxiv/...=1#post4829920

Well, this event, with BLUs around, shows a good example of balance of the game being broken.