Sure. There are encounters that are light on healing. But how about the ones that are heavier on it?
Should we ignore those?
Edit: Forgive this, but I have other forums I want to discuss things in, so you're only getting this one, lest I hit my daily limit.
The same reason tanks have mitigation cooldowns despite not needing them for the majority of content.
Just because it isn't used in -ALL- content doesn't mean it isn't useful in some.
This is also a matter that addresses a more subtle part of the damage / healing dichotomy, and that's decision making. By attaching Misery to healing GCD use, it means your big pay off wtf White Mage foul has inherent opportunity cost, and finding those areas where you can minimize that cost to maximize your gain becomes a facet of your gameflow.
Wasting your lilies to heal something that isn't there means Misery is, at worst, "Not worth it". Utilizing your Lilies, recognizing when you cannot OGCD or when you shouldn't, when you should Regen vs "Cure 2" as a spot heal, or a maintenance heal, leads to a bigger pay off. As an earlier poster mentioned, you're more likely to use Medica over Cure 2, primarily because Assize is usually not used to respond to damage intake, Cure 3 isn't useful in spread scenarios, and medica 2 shouldn't be spammed.
Also, my previous math was a little off in a prior post, primarily because Regen's potency may have changed.
Using the tooltips we have (which are not final but no reason not to use them), Regen is a 1200 potency heal over 18 seconds while AffCure is 700 / GCD.
We can extrapolate this out with 2 Regens being worth more than 3 AffCures.
So long as there is no overhealing on either, this means 2 Regens have a potency loss of 300 over 3 gcds. (2 Glares lost, 1 Glare gained) compared to 3 AffCures being a potency gain of 675 (Each Misery is 900 potency over 4 gcds, or 225. Using Afflatus to heal instead of another GCD means you bank +225 potency to cash in when Misery is finally used).
If there is zero healing, then every AffHeal is -75 potency (225 banked potency - 300 Glare) because that's a glare you should have used instead.
So, sure. Some encounters you never use a GCD heal. But I'd reckon in most you're still using regen.