I (mostly) solo leveled Blue Mage to 50. I hunted world skills. I've gotten the non-EX/HM dungeon skills. I beat Masked Carnival 25. I have done the content as presented.
TLDR: 6/10
To call it side content is simultaneously unjust and incredibly accurate. It -is- side content, but was at least done with a faithful representation of what Blue Mage is supposed to do, to a degree. In this regard, all of SE's side content is done to some amount of polish, even if they can be shelved the day after it comes out. The Job quests are about on par with what standard ARR jobs got.
What Blue Mage does right
Presentation, flavor, and rooting itself within the game world. Blue mage not only feels like it belongs, but the bits of story we are given feel like a natural placement for how it would fit within the world of FF14.
The skill animations are good, the player animations fit the pomp and flair of someone set to perform - Which is the Blue Mage we are given here.
Some new skills feel fantastic to acquire. Their current implementation does justify keeping Blue Mage out of party as they allow for dumb things to happen. (However, I would rather have Blue Mage made for regular content)
What Blue Mage Does Wrong
Progression
Obviously this more open ended skill learning is bound to mean that we can't judge Blue mage progression by our standard, right?
Right. Obviously. And I'm not.
I'm judging it by the standard Blue mage has set for itself. The idea of a lateral toolkit that you change to suit your needs and wants.
It has not succeeded in this regard. In many cases, the enemy skills you learn as Elemental-swaps of each other, or are straight up superior to previous skills. There are minute differences between them, but these differences require caring about High Scores in the Masked Carnival to matter, at all.
Here's a typical example.
Mindblast compared to Ram's Voice, Mindblast loses in every scenario. It loses in CC, it loses in range, it loses in damage, and it loses in potential interactions. Mindblast would be completely irrelevant except for two reasons.
1. Tightly packed ice immune enemies in the Masked Carnival
2. You literally need it to advance the Blue Mage quest.
For the first, this only matters if you're going for a bonus (Caring about the high score) instead of just using another AOE that is both superior, and can exploit a double damage weakness.
For the second, there's a video series that explores this style of game gating, and it's rarely favorable. If I could unlearn mind blast after doing the Blue Mage quest, I would. As it stands, a majority of Blue mage's abillities are not interesting in mechanical use in the overworld (Where you spend most of your time), but the Masked Carnival at least gives them relevance.
But you can also mostly just spam Glower or Drill and be just fine.
The Masked Carnival also presents more annoyance than challenge. Rather than giving you 'challenging fights' that you can excel with by picking the right toolkit, you are given fights you literally cannot win without having this one specific blue magic spell. I could have beaten the last round of Masked Carnival the moment I unlocked it except I was missing two skills.
It wasn't creative use of skills to win, it was mandatory, thus cheapening any sort of puzzle element towards the encounter. From a progression standpoint, this didn't quite bring the encounter clear catharsis that I usually get. I honestly came out of it more frustrated with clearing than when I entered.
I will add a slight addendum here that I do not have -every- skill, and it is entirely possible there are unmentioned interactions that play further into the Masked Carnival, but I do doubt it.
There is also apparently no basic wind spell, yet wind resistant enemies are basically in every stage of the Masked Carnival. This is a heavy oversight as every other element and non-element is represented outside 5 ranks, except Wind.
Conflicted Focus
Blue Mage is touted as a more solo oriented playstyle, and the primary reason it cannot be put in the same realm as the others. For this reason, and the unique skill learning, it cannot be allowed to casually pug with even outdated content - As it not only breaks the content, it can also be a giant hindrance.
But then immediately afterwards, half of your skills come from dungeons. Stuff you cannot solo as a blue mage. You must either band together with other blue mages, or convince a friend to come with you to help you out.
????
So in order to gain our skills for our job that can't play nice with parties, we have to...form parties.
The most overpowered abilities of the Blue Mage are also the least satisfying to use. Stripping that away turns Blue Mage into one of the weakest classes were it not for the inflated basic action power (50% increase) and the complete lack of interesting -damage- spells.
"Low accuracy" skills basically translate into "Spam it until it works". Spamming stuff until it works doesn't go great for capitalizing on advantage windows, of which every single DPS job is designed around, especially with one of those "Spam it until it works" skills is akin to an auto kill.
Skill interaction isn't only minimal in number, but in potency. Why would you Aqua Breath into High Voltage? That's two skill slots for a weaker effect than double Ram Voice, or Flamethrower, or anything else. If your goal in the Masked Carnival is to exploit these skill interactions, then they, you know, need to be worth using over double Glower.
The entire reason they were excluded is because it was touted that they'd break content for everyone else, and I'm over here thinking that now I have a little bit of what the people who bought Fallout 76 felt when they stepped out of the vault.
How to improve Blue Mage Within Its Current Scope
This is not about making it a full class. That is what I want. However, this section is primarily about improving what we have right this moment.
Skill variety. Everything is a spell. Even the OGCD is a spell. Every attack spell is a palette swap of another. Some diversity here really would fulfill the promise of creating interesting toolkits, such as:
More melee attacks (Goblin Pauuuuuuuunch)
Proper OGCD abilities (Loom should be in this category, to really make Ram/Dragon combo flow)
GCD variation (Slower speeds, faster speeds, create more interesting action dynamics)
Blue mage is literally the canvas that SE can test out mechanics to implement on other jobs, and yet it somehow has the most bland kit out of all of them, just being this disjointed mess of stuff you just eventually stop using because Glower Spam is best.