Well, I'm lv10 and I'm bored already. Not saying my opinion is supposed to invalidate this content, but this clearly isn't my kind of content.
What I know is that some arguments made previously in favor of Limited Blue Mage have been kind of dropped. As I though, what they were saying with "identity" was never about the "we have to have all the classic skills in Blue Mage, and they have to be faithful to their classic effect and/or to the mob's version of the attack, and that's why the Blue Mage would be OP in regular content", it was just about "Blue Mage collects skills from monsters, regardless of whether they're the classic Blue Mage skills or not".
There are a few classic skills missing afterall, from what I looked into: Goblin Punch, Matra Magic, Angel Whisper, Frog Song, Blaster, Acid, etc (not saying they might not be added in the future). And the spells are not even exactly the same as the monster version, from what I've heard. It's all about collecting skills from monsters. That's the "identity" part of it. And if that's the case, the excuse of "the spells are too OP to be balanced, or if they are nerfed too much they won't be the same classic spells and it won't be faithful to Blue Mage" doesn't seem to hold much water. Speaking of which, I spent most of my time as Blue spamming Water Cannon, because the other skills I collected seemed mostly useless. Maybe I was playing it wrong. It's most likely. But I still don't feel invested enough to spend much more time doing this, especially when people say that it gets worse when you have to start going into dungeons and Primal EX, so it's a pass for me.
But I'm lucky that I can use my favorite FF classes (Samurai and Dragoon) in regular battle content (and most importantly the MSQ). I can understand that those that had Blue Mage as their favorite feel very discontent now.