Anyone who has been playing for a number of years remembers all of the BLM specialists that used to run around. There were Tarutarus that simply had everything that BLM could possibly get and always showed up to events on BLM. They were very welcome too! We used to have to kite Kirin around for 30 minutes while the BLMs and SMNs chopped away at him and the MNK was stuck Chi Blasting for 3000 dmg every 3 minutes. Now I'm not saying that all content should exclude major melee DD jobs, but all content should not make BLM obsolete either. There is currently very little use for Meteor, Kaustra, Helixes and even general Elemental Magic spells. So here is my suggestion:
Add one major mob, on the scale of Odin V2 or Arch Dynamis Lord and Pandemonium Warden within the new expansion, that takes magic damage at the normal rate of what a level 110 mob would, but takes little to no physical damage. Then give it ridiculously strong attack power so that only a Paladin or Ninja can tank it. Don't put a time limit on the fight but have multiple force spawn locations in different rooms, and make the mob drop Meteor among other very good items for mage and some for melee.
See what I'm getting at yet? Yes I'm asking you to do what many (not all!) players have asked for and bring back the strategic style of play. A lot of people are tired of 45 second fights on what is considered to be the hardest mobs in the game, and they also have nowhere to use/show off any of their mage gear. Even white mage is boring now because they never run out of MP given the short fights.
I am in a Nyzul static and no one even cares about Nares gear even though it is some of the most amazing mage gear this game has ever seen. We will all end up getting it, but it's really just for future planning in case new content is released that uses mages.
I'll stop there because the amount of people that read posts is inversely proportional to the length of the post, but let's hear your thoughts and hopefully the Dev's can get a response in :-). (please say that revamping black mage is on the list after the jobs you're working on now)