Honestly, the only big problem with BLU is that its content needs people, and it's because of how much time you need to grind to have it set up. (Which imo, is fine. But the playerbase hates grind so...)

BLU with all the spells is actually a very fun job, and is pretty much the most fun synced down job in the game (cause you're not losing skills).

On paper, it pretty much gave the game a bunch of things that the game needed:

An incentive for doing old content synced, and even min-ilvl no echo.
Literally something to do and grind for, which the game needs a lot more of.
Completely different playstyle for all 3 roles, Tank, Healers and DPS.

It really just needs more people trying out and doing BLU content, especially during content droughts like this one.