Channel Divinity: Preserve Life Does Not Work

Read the description. Preserve Life only gets your character up to half health, so its not a general purpose heal. It's better used on a very low health or downed character.

The ability should not allow you to select an invalid target, or should not be consumed if activated with no valid targets.

I made the same reading failure roll pointed out by J above. I would like to second Guurzak's helpful suggestion. Most spells let you know if you try to select an invalid target.

I believe it's not the end of the world to let this ability be used in this case, as the target is not technically invalid - there are no rules preventing you from using the ability on such a target, it's just that it has no positive effect. And what did you expect when using something without reading its description?

Yet, the error message "Character is already at full health" in this case is clearly incorrect and should be reworked.

I believe it's not the end of the world to let this ability be used in this case, as the target is not technically invalid - there are no rules preventing you from using the ability on such a target, it's just that it has no positive effect. And what did you expect when using something without reading its description?

Yet, the error message "Character is already at full health" in this case is clearly incorrect and should be reworked.

I misread the spell description and thought it would heal up to half of the character's total HP on the resulting roll. I didn't realize it meant that the spell will only be valid if the character has less than half of his current HP and the resulting text certainly didn't help.

So, it's not so much a matter of not reading but incorrect comprehension. The resulting text should be clearer in any case, or the target should be considered invalid.

I agree it should just show an invalid target then (or at least rewrite the log message).