Can we please just throw out the idea that making players think at all will scare them into quitting entirely? It's a stupid idea, and I'm tired of dancing around the issue.
Take a look at any competitive game at all, and you'll see mountains of people who put in the time and effort to master every little nuance of their game. Why do they do this? Because it's fun of course. And every person who is good at the game was once a lowly level 1 struggling to keep GCD uptime against world mobs. It didn't scare them away, and the fear that it might isn't a good reason to ruin the fun for the rest of us. Can we stop pretending that having the same exact damage rotation from level 4 to level 100 is a good idea for a difficulty curve? What are people even doing through leveling if not learning how to play their class properly?
Furthermore, so what if a few players go "oh, I can't wrap my head around this. it's not for me"? Nothing can be for everyone. Not even this critically acclaimed MMORPG with a free trial up to level 70. Maybe some people just don't resonate with healers as a concept. Maybe some people just don't like tab targeting hotkey based combat. Are we going to start getting worried about losing out on that demographic and change the game to a first person shooter instead? And What of the healer main who watched their favorite role getting lobotomized into the ground to appeal to people who don't even like healers in the first place? Aren't you glad that you put in the time and effort to develop your skills in healing only to have some floor-licker whine about it being too hard, only for Square to decide that this is the mindset we need to cater to in order to create a better game.
My point being, People can adapt to a lot of things. Having a bit of complexity, or even a decent amount of complexity isn't going to hurt anyone. On the contrary, it will foster a large amount of dedicated players who put in the effort to squeeze every last bit of optimization they can out of their chosen job. Meanwhile, the casual who doesn't care about playing properly will just continue mashing broil and physick because they like the animation and don't care to read tooltips. This player isn't planning to play Extremes, Savages, or especially not Ultimates, So what does it matter that he can't be the best?
Also, Even if this casual player gets scared and logs off because pressing more than two buttons puts him into an anaphylactic shock, Why can't he just go play a different class without a complex rotation?
Seriously, we've got Gunbreaker and Dark Knight, which are known as the busy tanks as opposed to the simple tanks of Paladin and Warrior. Why can't we have White Mage be the simple healer with a simple rotation, and if you want complexity you play Scholar, Sage, or Astrologian? Remember, the main damaging rotation on all four healers right now is exactly the same. The only difference is that they get an extra button to press around burst windows, and Sage gets Phlegma, which you press twice every 80 seconds. riveting.