I don't think that really is the assumption though. The baseline of 6-8 encounters per day is predicated on a certain amount of difficulty per encounter (not very difficult). The real assumption, to balance long and short rest classes, is 2 short-rest per long rest. This means the real "requirement" is 3 encounters per day (with a short rest between each encounter). However, if you want to keep the same daily challenge as 6-8 encounters / day, you need to increase the per encounter challenge.This is sadly true. 5E was built around a set of assumptions on encounters per day, and this assumption doesn't match actual play for most groups.
If you're not seeing 6-8 encounters per day/LR - talk to your DM. See if that is something the players and DM want to try out.
If you're not seeing 6-8 encounters per day/LR - talk to your DM. See if that is something the players and DM want to try out.
If you wanted to get the same effect without eating the caster’s reaction every round, you could even just say it can only heal once per round.I must say, I agree with @Charlaquin, the spell as originally released was somewhat broken, or at least very overtuned, in that it was vastly more effective out of combat and dwarfed other spells in a similar niche. We had tried a fix, pre-errata, that required the caster to spend a reaction to cause the Spirit to heal a creature in it's space. This seemed to curb the "conga-line" and out of combat issues, while only minimally hindering in combat usage.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.