I only recently got BLU to it's current level cap and because I didn't do it when it first released it doesn't seem to be that easy to get parties to go into dungeons to help get the new spells. I'll probably just not bother getting all the spells since they are probably just copies of old spells with new stuff anyway. They could easily let BLU use Duty Finder just by making it so you have to have a certain number of spells to do x dungeon. And they've proven they can make some spells not work in groups with Basic Instinct so I don't know why they couldn't grey out some of the more broken spells when you use the Duty Finder or when you are not in a party of all BLUs.