Healing Spirit is fine RAW

[Tanarii]

The point I think Tanarii was trying to make, however, is that a spell that heals 5d8 outpaces an enemy attack that deals 5d8 damage but has a chance of missing. Which is simply true.

Indeed.

It may or may not outpace the damage prevented by inflicting 5d8 damage with a chance to miss yourself. Thats more complicated, because it depends on enemy HPs.

Otoh number of enemy actions cancelled is much easier to figure out, if you onow their damage and chance to hit vs a target. And against one attacking your tank, it can be a lot.

[qube]

Indeed.

hey, you even didn't take in the resistance dictomy. Resistance is quite common over vulnerability (esp. on the player side, with barbarians , HAM, a rogues half damage thing, etc ...) .

including that empowers the efficiency of healing even more over damage.
(5d8 on a barbarians is heals the equivalent of 10d8 damage; healing 5 hp on a HAM fighter could heal 5 attacks of 4 damage each)

[Willie the Duck]

I think that interpretation seems unintuitive, artificially adds an in combat vs out of combat state which exists nowhere in RAW and likely causes more problems than it solves in terms of other spells you might cast, where the interactions occur during actions or bonus actions on your turn.

The argument is older than dirt (or at least approaching disco in age). Magic Missile, when introduced in Supplement 1, did not have a listed duration. However, in I believe in 1e and Holmes, this was changed to 1 turn (10 minutes). In combat, this meant you didn't have to launch all your missiles at once, or even launch any the first round. Some interpreted that as meaning that you could cast it before someone kicked in the door and thus before combat. Thus, you were free to launch them at anyone on the other side without the chance that someone could disrupt your spell. Others argued* that stuff didn't happen in rounds outside of combat. Thus, before the door was kicked open, all actions took a full turn, meaning that the spell would expire before combat would begin.
*If you ever wonder what people could still be arguing about on classic-D&D-focused forums like Dragonsfoot, this is it.

In both that case and the one in 5e, there is language in the book that indicates the things aren't measured in rounds outside of combat (or similar situations). However, they have never been consistent about it. Without looking, I can confidently say that there are things in all editions that are only rules-defined as operating within the round structure that one could conceivably want to attempt out of combat. Regardless, even if they had been consistent, as you point out, it is unintuitive and adds yet another sense artificiality to the game. So I agree, this argument doesn't seem to add value to anything that instead altering the spell a bit wouldn't do better.