Ifrit actually gets increased damage from ice in many (most/all?!) Final Fantasy games, so black mages instead of being "neutered" in that fight, would be glass cannons with no down-times for their heightened offense, as blizzard spells would deal increased damage just like fire spells do normally.
Also, due to how all jobs that have elements (not counting Holy since Holy and Dark are elements that are rarely resisted in Final Fantasy games...outside of undead absorbing the latter) have more than one element and usually two consecutive in the wheel, it's actually not terribly bad at all.
However, there is little to no chance of that in Final Fantasy XIV. The developers have proven to want to remove anything at all that requires planning or customization, and how materia is limited in stats (you can't add a stat that is already there at the "cap" for the item level, and seeing as that usually includes all the "good" stats you would want in the first place, your options to customize are actually barely more than zero), they prove to not want players have any part in making the games balance, outside of their playing skills.
As an RPG fan (and fan of Final Fantasy series) where there are many options at any stage of the game, this design is a real pain in the ass, but other than that, the game is very enjoyable...so meh. Gotta deal with it.