Is this homebrew "Shimmering Barrier" spell balanced?

Question

I'm trying to make a spell based on a scene from the Dungeon and Dragons movie where a spellcaster protects a group of people around him with some sort of magical barrier:

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Shimmering Barrier
2nd level abjuration
Casting Time: 1 reaction, which you take when you or an ally within 10ft rolls a saving throw.
Range: Self (10-foot radius)
Components: S, M
Duration: 1 round

A shimmering barrier of light envelops an area of 10ft radius centered on you for a brief moment. You and all friendly creatures in that area receive a +1 bonus to all saving throws until the start of your next turn and 1d6 + your spellcasting ability modifier temporary hit points.

At higher levels: The number of temporary hit points increases by 1d6 for each spell slot above 2nd.

Classes: Artificer, Bard, Cleric, Druid, Paladin, Sorcerer, Wizard.

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I'm not sure if the wording is right, but the intent of the spell is that every creature that was in the area of the spell when it was cast will get the +1 saving throw until the start of the turn of the caster, very much like the Shield spell.
Also, I'm not sure if I should word it as to allow it to be used after the saving throw is rolled but before the outcome is determined. Shield works like that, I want to keep it simple so maybe I should.

I think that the game is still lacking a lot of abjuration spells and this would fill the gap of a niche way to help the party when they're caught together into some AoE damage or effects.
I feel like this would be a good 2nd lvl spell or a weak 3rd.
I included pretty much every single spellcaster class because I want to encourage teamplay, I think it's pretty neat when the players help each other with support spells.

Answer 1

This is a strong level 2 spell, 3rd might also be OK

I think you got the leveling right. Here's why:

Another spell that provide similar benefits is Enhance Ability (level 2), Bear's Endurance for 2d6 temporary hp and advantage on a constitution check. That effect is pretty comparable. Your spellcasting modifier is likely +3 or +5 at least over the first 11 levels where most play happens, for 4 average, very close to the 3.5 average from the second d6. The advantage has a higher numerical effect than +1, but the saving bonus applies to all kinds of saves. The duration of Enhance Ability is up to one hour, but it hogs concentration. Being able to use the effect as needed with a reaction is likely a bit better, as the temporary hp go away when you are hit anyways.

The party often is standing close to each other, so for a typcial party of around 4 characters, you can likely expect 3 or so to benefit from it, or use the guidance in the DMG recommendation on p. 249 of radius/5, here 2 targets.

Since your effect can cover 2 or more creatures, it also could be level three, like an upcast Enhance Ability to 3 that also can cover 2 creatures or to 4 that can cover 3. However, upcasting typically is weaker than a spell that is native of that level, and enhance ability is a pretty weak level 2 spell to begin with that I see rarely used, so the level 2 you provided is probably OK. In this case it would be a strong level 2 spell.

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P.S. You might consider the actual ability that Simon Aumar from the movie has in his official, published character (available here), also for the wording:

Sheltering Shield (3/Day). When Simon or another creature he can see within 10 feet of himself would take damage, he conjures a shimmering, 10-foot-radius sphere of magical force centered on himself. Creatures inside the sphere have resistance to the damage that triggered this reaction.

He is not built like a PC would be, but his highest level spells are Bigby's Hand (level 5) and Major Image (level 3), each of which he can cast once per day. He can cast various 1st-level spells twice per day. So this version being available 3 times means it would likely be a first or maybe second level spell. Resistance can easily save you as many hp as 2d6 against something like a fireball, or more if you do not save. This version does not also provide a bonus to the save, so it is a bit weaker at least in the lower levels until you run into opponents that deal lots of damage, and I'd peg this one at level 2 too.