Considering we got two DPS in Stormblood, people would have been upset if we didn't have healer/tank for SH...although to be fair, it's not actually confirmed we'll have another healer
On another topic, the more I think of it, the more appealing it feels to replace gear with spell hunting for BLU. It would break the mold of grinding tomes every 6 months, and you could still aim for the same content, with some skills being available only in Savage on even patches, and in the next 24-man raid, exactly like the upgrade system for gear. You would replace obsolete spells the same way you replace obsolete gear, for example replacing 1 000 needles by 10 000 needles, or even 100 000 needles in a few years, etc...And the spells you equip could have a corresponding "ilvl" that would work with the DF or RF requirement.