It has as much to do with how you are describing it as the adjectives you are using. Please don't assume my one word summary and differentiation by usage of differing adjectives is due to semantics instead of the meaning behind those words that you are conveying.
Just to make sure I understand, Are you saying you feel the "RAI" version is Overpowered and GameBreaking as well?
My position is that even the best out of combat healing spells (like RAW Healing Spirit) aren't as game altering as they are cracked up to be. Why? Well...
1. It's a spell and that makes it a limited use resource. This means that even in the worst imaginable case that there can still be resource drainage due to multiple encounters
2. There were already options to get back to full HP after almost any fight. They may have taken more spell slots (cure light wounds or prayer of healing) or they may have had a large drawback in time required like short resting or long resting or possibly using rope trick or leomunds tiny hut coupled with a short rest or long rest (but you gained more than just hp with these 1hr long and 8hr long options.
3. It's not effective to use during combat. This really can't be said enough because that means it will have limited impact on how most fights play out.
4. After any given battle if party is only injured enough so that other healing options can heal them fully then healing spirit isn't any better than those spells in that instance. Basically at least 1 character has to be greatly injured for healing spirit to really be worth casting. Being a level 2 spell it isn't a great option if a couple of members of the party are only lightly damaged. It will heal them yes, but it's an expensive resource to use to do so.
If there is any contention on these points I can elaborate on any of them a lot more.
Let's look at a potential in game scenario that you think highlights healing spirit as very detrimental. You believe it's really bad in games where many encounters are meant to wear the party down. Let's look at that situation over 6-8 encounters. Assuming a party of 4 characters at level 3. I'll assume a Fighter, Rogue, Wizard, Druid.
Encounter 1 - Easy
The fighter took 7 dmg. No one else was injured.
(Healing spirit would not be used here. Instead goodberry was used)
Encounter 2 - Medium
Fighter took 10 damage. Rogue took 5.
(Looks like another good berry). The fighter will be down 2 hp from max. The rogue will be maxed.
Encounter 3 - Hard
The wizard and druid each lost 10 hp. The rogue lost 12. The fighter lost 15.
(This would be a great time for healing spirit, but the party is probably interested in a short rest at this point if possible to restore other resources than just hp). So the party short rests and primarily uses hit dice to get an adequate amount of hp.
Encounter 4 - Hard
The party again loses the same hp values as the last hard fight.
(Seeing as their was just a short rest and hit dice are low this is a good opportunity to use healing spirit). Keep in mind a life cleric at this point with prayer of healing would be almost just as effective given at healing as healing spirit).
Encounter 5 - Easy
A small amount of hp lost. Another goodberry here covers it.
Encounter 6 - Medium.
A moderate amount of hp lost. Goodberry here covers it as well.
Encounter 7 - Very Hard
Everyone is near death at the end. To get through the fight the druid casted moonbeam/spike growth. (Druid is now out of spell slots).
Party decides to long rest.
_________________________________________END SCENARIO!
Is the usage I just described of it game breaking or overpowered?
Healing Spirit clearly overshadows Prayer of Healing, and I would say it also overshadows the 6th level spell, HEAL.
Heal does 70 hp to a single creature. Even cast alone without the benefit of Beacon of Hope, Healing Spirit will average 35 points of healing to each creature. Your party has more than two characters in it? Congratulations - you don't need to "waste" that 6th level spell slot you can instead use a second-level spell slot.
With this in mind, Healing Spirit could easily be a 7th level spell.
(Seeing as their was just a short rest and hit dice are low this is a good opportunity to use healing spirit). Keep in mind a life cleric at this point with prayer of healing would be almost just as effective given at healing as healing spirit).
Ok so your points 1, 2 and 4 are all great points that would apply to a first level fireball that did 30d6 of damage too?
1 - its an expendable slot.
2 - there are other options to do damage and win fights to other than this mega-bomb.
4 - for critters where the attack is overkill, like the healing, its just overkill so no better than a weaker damage amount that still dropped the bad guys.
third is not so clear.
3 -also it only works in combat so while it will help in one fight, it wont help get ready for the next or fly across a chasm or turn us invisible or any other of numerous things a fireball isn't good for.
As to the rest, I am so very thrillingly glad you can describe a hypothetical case where it did not cause an imbalance. that reinforces my argument that in some cases in some types of campaigns etc it wont be a problem.
just like the mega-fireball at first level wouldn't be a problem in all cases in all campaigns either.
As for whether or not the new reversion to their intent is [insert various descriptors] it reduces the total for the base spell and its other versions quite a bit and definitely helps bring it closer in line... but it leaves a very out of whack scaling multiplier effect that seems to me still a big red flag. i do not know how bad it would be on your own personal adjective spectrum and would not want to even try to dive into that word salad, so i will just say i would NOT allow even that version in my games because of its broken scaling. Additional "ticks" or "hits" of healing should be added as it levels off, not dice per tick.