You had to track all of those things... even with the extra dots or unique buffs from cards.
Tracking OGCDs are not difficult. The game gives you a flexible UI that you can slot in those pretty icons that happen to show you cooldown time.
Can a GCD be life or death? Yes it can. Will it be most of the time? No.
Need to work with a co-healer? You will adjust or they will. If you are unsure of your co-healer, bring your own.
I am not even close to being the world's best healer in FF14, but I even know that we have regressed as a class (oddly enough in a game where progression is vertical). It is honestly insulting.
Especially since none of those things you mentioned are even hard once a player gets used to the basics of the class and content. This game is so forgiving on casual and mid-core content. Tracking things in FF14 shouldn't be hard for healers in this iteration.
Especially when I can recall all of the things we had to track manually in FFXI. Each spell in FFXI had their own cast time and cool down. There were no pretty icons. You had to either pop open your spell menu or used /recast <spellname>. GCD didn't exist. No passive mana regen either, you had to
/heal or rely on other players with a Refresh ability/spell, rare/expensive gear, Ethers, or Juice. All the while manually tracking buff timers because there were no icons to show you what buff someone had (you only had the combat log to show you when something falls off) and standing in what you may think is a safe spot because enemies didn't place orange markers for mechanics (you had to guess/know). Oh, and wipes mean you lose hours to months worth of progress (counting on the content and the player). Wipe in an exp party: WHM may be a few hours loss of progress, DPS could be weeks due to wait times. EXP parties are casual content in FFXI.
Now my back hurts, great. Where's my walker and blue robe?