I put in bold the things that will still matter, but they are within the context that fights in this game are scripted. Bosses mostly do mechanics in the same order every time, so once you are used to the order, there isn't much in the way of reflexes, multitasking or adaption unless one of your party members does something wrong.
No, it won't, and it was already made less complicated in recent years:
- An ability was added to keep up Ice phase out of battle which you had to spam, then it changed to be available at lower levels, then it changed to lock out of battles so you don't need to spam it.
- The AoE combo became more consistent and able to switch between AoE and ST easier.
- It highlights what to press next (did not used to, which made it one of the hardest to figure out rotations).
- They made Enochian upkeep a trait years ago, and are now doing so with the timer, which is the thing that you're prevent from expiring - so it makes it as easy as Red Mage, Summoner and Pictomancer. This is about the last job that had such a mechanic (most jobs used to have this).
- The cast times are being reduced to allow for movement, making it as easy as Red Mage or Pictomancer.
- More things have been made instant cast in the most recent expansion, and we'd already got Triplecast years ago.
Point is, they have made jobs easier and less stressful over the years, and Black Mage has been the last bastion of that, until the 25th.