Did the devs explicitly mention that BLU can't raid?

[Zakon]

See, this Yoshi P talking, so we need to read between the lines. Remember he said "We said that BLU does not fit into XIVs system, but we didn't say we wouldn't add it", and "We said that adding a new job during a patch would be too much work, but we didn't say we wouldn't do it".

Nothing he said here contradicts their stated goal with Blue Mage.

They didn't think Blue Mage would fit into XIV's system... so they made a special system designed specifically for them, separate from the other jobs. A "limited job" that is designed for solo play.

They never said they wouldn't add another job mid-expansion since it was so difficult, so they didn't. They added a minigame dressed up as a job. It didn't take dev time or balancing because it isn't designed to play like other jobs or be balanced to begin with.