It's more than a bit ridiculous that Blue Mage is going to have access to our top tier spells (because Curaga V is going to be completely excessive, Cure VI is currently less so but certainly an OSHI- button). However, the difference is that Blue Mage has a completely different role to Red Mage. In practice, what party is likely to ask a Blue Mage to heal for them? Yes, it does happen, but not often.

Red Mage, on the other hand, generally has a very similar back line role to White Mage in most parties. If Red Mages had access to Cure V they would immediately be using it to augment their existing role and would therefore be better positioned to start giving White Mages something to worry about.

I'm not saying it's right for Blue Mages to have these spells, or that Red Mage shouldn't get something decent to help with healing, I'm just pointing out a possible reason why White Mages aren't foaming at the mouth over this sort of thing.