How can I reach my full potential as a healer?

[Taika]

White Mages don't need crit. In fact, it's more of a terminal disease for white mage than anything. In most cases, a crit cure will overheal for the amount you gained from the crit. In the case you use a Cure II and fully benefit from the crit, you're healing way too late and the tank might actually be dead already.

I disagree. In many if not most cases, crit will only overheal if the WHM is already overhealing. Crits can help with keeping tank up with only Cure 1s and regens and they're a blessing with rare AoE heals and Medica 2 regen ticks. I personally feel crit helps my MP management as I aim for minimilised healing in all fights I do. I do not have enmity or MP issues. My secondary stat priority is DET > CRIT > PIE > SS, but I don't have my BiS set yet.

Aaaand it was pretty cool to see my cure 2 land with 5710 HP on tank! Of course some of it was overhealing (tank had a bit under 6k of 9,7k and SCH hit adlo at the same time), but I don't think anyone can make each of their healed points count. And hits like that able me to heal with mostly Cure 1 and regen otherwise.

As for topic, to be an excellent White Mage, I think most important thing is to know the fights well and plan your healing accordingly. Be aware of how much damage is coming through and how to get through it with least possible MP spent while keeping everyone safe. A great WHM is able to heal effectively and pre-emptively, land their stoneskins just before a big hit lands and their cures right after it has landed. I take videos of my healing when I'm learning the fight and plan my healing based on what I actually see happening, not how I imagined it went (I tend to be very tunnelvisioned while learning new fights).

What is more difficult is being able to deal with unpredictable damage and deaths at the same time, caused by party members making mistakes. That's also a big part of being a great healer: being able to pay attention to your surroundings and other party members and make fast decisions to save the day when things go wrong.

Another important thing is communicating with your cohealer and tank(s), other party members too of course. Coordinate your heals, buffs and cooldowns so that you support each other and work in synergy. If you heal everything as if you'd be solo healing, or if both healers focus on only AoE healing while tanks are going down (or the other way around), it's not effective healing.

And finally, maybe the most obvious one: know your abilities and use them effectively. Especially Shroud of Saints, Divine Seal, Eye for an Eye and Virus should very rarely be off cooldown. Presence of Mind is great for situations that need fast healing, stoneskining whole party in T9 or casting Stone II / Holy to help with damage. Benediction should rather be used too often than too seldom. Surecast and Fluid Aura are the only abilities I don't really use regularly, but they aren't useless either.