It sounds to me like you're holding onto a hope that Blue Mage is in a live beta and will slowly become a fully fledged job over time. However that isn't how Square has presented the job. In their official statements they've described it as "Not suited for parties" "Designed for Solo Play" and unable to enter content such as PvP, any matchmaking, any roulette, or even deep dungeon and they gave no indication any of that will ever change.
If Blue Mage was simply in beta, with the intent of being slowly integrated into the pantheon of jobs available and we were told as much then I don't think there would be a "delete limited jobs" crowd at all. We'd all be for it. A beta period is worth having fascinating jobs in the game, but that isn't what this is. What this is, is one of our favorite jobs being added to the game as something that both is and isn't a job in the game, half a job with no use in most of the regular content that we enjoy in this game, with absolutely no hope for anything otherwise being offered by the developers.