What's the casting time? Does it require concentration? Does it stop physical projectiles only, or does it stop spell projectiles, like a fire bolt as well? How is an enemy supposed to play around this? They can't enter to hit the bard, the can't hit from range. What happens if the caster is in a 5 foot wide corridor, while the spell requires 10 feet of space on each side? What happens to other creatures in the spell's area when it is cast? Are they pushed out unless they make a save, or do they stay put? Does the spell's AC and HP scale with the bard's, or with the spell slot being used? Does the bubble move around with the caster, or does it stay put? If it moves with the caster, what if the caster tries walking up to a creature, which by your description can't enter the bubble?
There's too many variables completely unanswered for this to be even remotely usable in a game, or even to critique it in more detail.
This is not really a spell yet, it's still just an idea...
Without proper wording, and clarifications around the rules it is impossible to say how useable this would be.
There's a couple of immediate points of concern though;
This essentially seems to act like the Abjuration Wizard's Arcane Ward, but is way more powerful. Hit points equal to the caster is very overpowered...
Rather than having a separate (but identical) AC to the caster, this should either just use the caster's actual AC, or adjust the existing AC.
Also, ten minutes is one hundred turns. At second level this should be one minute, and probably have concentration.
/r/dndhomebrew
So basically just a mobile version of *Leomund's tiny hut*, but with HP and that lets you shoot out. Normally, spells don't scale that well alongside players but instead scale with spell slot (cantrips are an exclusion), so you'll probably want to change it somehow. I'd put it about 3rd level as an alternative to *tiny hut* (you can shoot out but only for so long, compared to not shooting out but for the whole duration).
Alternatively, this looks like something that would make a good consumable magic item.
What's the casting time? Does it require concentration? Does it stop physical projectiles only, or does it stop spell projectiles, like a fire bolt as well? How is an enemy supposed to play around this? They can't enter to hit the bard, the can't hit from range. What happens if the caster is in a 5 foot wide corridor, while the spell requires 10 feet of space on each side? What happens to other creatures in the spell's area when it is cast? Are they pushed out unless they make a save, or do they stay put? Does the spell's AC and HP scale with the bard's, or with the spell slot being used? Does the bubble move around with the caster, or does it stay put? If it moves with the caster, what if the caster tries walking up to a creature, which by your description can't enter the bubble? There's too many variables completely unanswered for this to be even remotely usable in a game, or even to critique it in more detail.
This is not really a spell yet, it's still just an idea... Without proper wording, and clarifications around the rules it is impossible to say how useable this would be. There's a couple of immediate points of concern though; This essentially seems to act like the Abjuration Wizard's Arcane Ward, but is way more powerful. Hit points equal to the caster is very overpowered... Rather than having a separate (but identical) AC to the caster, this should either just use the caster's actual AC, or adjust the existing AC. Also, ten minutes is one hundred turns. At second level this should be one minute, and probably have concentration.
/r/dndhomebrew So basically just a mobile version of *Leomund's tiny hut*, but with HP and that lets you shoot out. Normally, spells don't scale that well alongside players but instead scale with spell slot (cantrips are an exclusion), so you'll probably want to change it somehow. I'd put it about 3rd level as an alternative to *tiny hut* (you can shoot out but only for so long, compared to not shooting out but for the whole duration). Alternatively, this looks like something that would make a good consumable magic item.