Classes that come out that are normal do not tell us they're "designed for group content," which showed BLU was meant to be different. And of course we didn't say "You SHOULD only solo" because that's not the point. For a class "Designed for solo play" I'd expect it to get its piece on its own.
I'm keeping the carnival opinion out since I actually haven't done that part of the content. It wouldn't be a fair opinion as I'd only be able to work off of word of mouth. However, I will focus on the "designed with a specific task in mind" part of this. Yes, it can work off of more than its original intended design, and it probably should, but focusing again on, "Designed for solo play," part. It does not feel like, to me, it did a good job being designed for solo play. For something to do more than it can originally do, it should be good at doing at what it originally did. Imagine if WAR did more dps, but couldn't keep threat anymore, at all, for whatever reason. Would you call it a tank anymore? It's still classified as a tank, doing, let's just say for funsies, a BLM's damage output, but it's not doing the job of a tank very well.
That's how I feel here. It's a class meant for solo play that isn't doing that solo play very well, outside of ONE piece of content.
Which my statement is also pointed out here. For a class that, in the picture, states it's designed around solo play, it's not very good at doing that outside of carnival and the gimmick spells.
Actually, you can't KNOW either way. I've had plenty of cases of players who were lacking their skills. In fact, I even ended up in a 60 dungeon on an alt with BLM forgetting to do any of my HW quests, removing almost half of my damage output. The difference is that, while I'm able to just do a quest for a skill, I have to go farm nightmare in Garuda EX because it's apparently more common than this spell.
When a mount I never even knew was a thing, and have most of the other ponies anyways, is more likely to drop than obtaining a spell that, outside of carnival, is worse than Ifrit's version anyways, there's a flaw in design of how common this spell is.
Also:
Both these images, also from the producer's letter on revealing BLU, show the BLU in Shiva and Garuda. In Shiva case, having the spell sure, but in both cases, ALONE. I wonder where people got the idea we could solo these?