Please, without comparing it to higher level spells (which offer things lower level spells don't), please show me how that's not balanced now.
Healing spirit heals, over time and at concentration cost, 3 or 4 d6 of hp at the level you get it (depending on if you're a ranger or druid, I'm assuming 14 or 16 wisdom). That's 10.5 or 14 hp for a second level slot, over time, at the cost of concentration.
Cure wounds, which is a very inefficient spell, cast at level 2 will do 2d8+2 (or 3), so: 11 or 12. It outheals the ranger's spirit, and narrowly underperforms the druid's. But cure wounds is an instant rush of healing. It also takes an action, so one must account for that as well, but the most key point here is that this is a spell that is slow, takes your concentration, and cannot be used in the vital ways that cure wounds/healing word can be used.
First, the opportunity cost. Here are some spells (won't go higher than 3) you could be concentrating on instead:
Heat metal: You'll do damage with no save, and if you target a weapon the target is either going to be disarmed or swinging at a disadvantage. One or two misses from that and you have out "healed" healing spirit, and done decent damage.
Spike growth: If you can catch even a couple enemies without strong ranged attacks in this at a bit of distance, you can stop them cold. At bare minimum it's easy to use to slow something down so it has to dash for a turn and take some damage. One ogre gets caught by this for one turn and you have outperformed healing spirit in damage prevented.
Summon beast: You have a pet with 20-30 hit points. You're either doing solid damage and controlling space, or it gets attacked and takes, at minimum, its hit points in damage. This spell is the same level as healing spirit.
Conjure Animals: And if you have this one, this is what you should be concentrating on. It lasts an hour, you should be able to get 3-4 fights of usefulness out of this. That's 3-4 combats you have a wall of meat to protect you in addition to doing top tier dps for the level. You can argue that this spell is higher level, and sure it is one level higher. But healing spirit costs the same concentration this spell does, and this one allows your team to win fights for an hour.
Almost any other option is better than healing spirit. A spell that is slow and eats your concentration needs to pay for that cost by being more effective overall.
But let's do an apples to apples comparison. Prayer of healing is a spell people always want to compare healing spirit to for some reason, but I think a closer, fairer example is aura of vitality. It's a spell that is concentration, lasts a minute, and is one that actually gets a lot of use, unlike prayer of healing.
AoV at Level 3, 20d6.
Healing spirit cast at 3, assuming 16 wisdom: 8d6.
But wait, it's worse than that, because aura of vitality is a better spell for other reasons. You can use AoV to yo-yo heal, you cannot reliably use healing spirit for the same function. So not only is AoV now overwhelmingly better at healing, whereas before the overtuned healing spirit outhealed it (and yeah, it shouldn't have), now AoV is superior in healing and in function. Tank falls down? Hit them with 2d6 healing, they're up. If you use healing spirit, you can move the spirit as a bonus action, but they are still down until the start of their turn. Better hope two kobolds don't stroll up and kick the tank in the face.
One might protest that healing spirit scales, and AoV doesn't. True enough. I do not think wasting spell slots of level 4 and higher on out of combat healing is ever a great idea, myself.