There's a difference though between how RDM plays and BLU being locked out of content. You being unhappy with how RDM turned out would be like me being unhappy if BLU was a healer.
Having a tank stance and at least one healing spell doesn't make the job a competent tank that can be the healer at the same time. RDM has a heal but it isn't a healer. An example would be me playing dancer back on XI and exping in the first jungle. We had a NIN tank that was awful so we booted him and I subbed war so I could be the tank. I was already the group's healer and puller then was also able to be our tank because of the type of enemy we were fighting. We just don't know enough about the blue magic spells to know if limited BLU will be able to fulfill more than one role at a time well enough that it justifies not bringing one of the current tanks or healers.
Why would SE have to make mandatory spells automatically learned? And how would having spells being necessary make it not a hybrid job? From what they told us, at least one MP recovery spell is going to be needed and the rotations will be about managing your MP. Sounds a little like BLM and DRK.
It wouldn't be time spent on one job and more like spending time on what would essentially be a separate job.
Why can't we push for that best of both worlds outcome? Or why be opposed to those pushing for that outcome?