Benediction is effectively useless.
The conditions to use it are basically:
- Healing target is within range (if you miss, you heal yourself)
- Healing target is less than 100%, but you're likely only ever to use it if the target is at 10% and that target is another healer.
Sure, you could use it to pull a Tank's ass out of the fire, but they're just going to die anyway if they're taking that much damage to begin with. You're delaying the inevitable by 5 seconds. It's best used when another healer is in trouble so they don't end up with 0MP if revived and become useless for at least a minute for them to recover enough MP to do something.
Maining WHM, this is what I do, and I suspect others do more or less:
- Do not Healbomb (eg Medica II, Medica, or Cure III) unless there is incoming party-wide damage. If you know the mechanics, you know to start casting before the damage hits so that the HP is recovered quickly. Proactively using Medica II just makes you a magnet for everything and the Tank has to re-gain enmity from you. Practice on Ultima Weapon.
- Use Cure I exclusively until there is enough damage being pulled to require a Cure II. This is why the number of mobs a tank pulls can vary depending on the healer. A healer that didn't minmax healing potency is going to not like the Tank that speedpulls.
- Use Regen on Tanks that pull more than one mob set. It however does increase the Enmity rate, so the Tank has to work harder.
- Use StoneSkin (or at least attempt to) before the Tank runs off to pull something.
- Use Protect before the party leaves the starting point.
Everything else in a party is generally not used except in a boss room. You shouldn't need to use Shroud of Saints or Divine Seal during trash pulls. If you do, the Tank is pulling too much or you are way undergeared for the dungeon. The CD's on these effectively make them not useful except for predictable boss room mechanics. Using them during trash pulls results in the Tank overestimating what can be pulled since the CD's are too long to use for speedpulls.