Leomund's Tiny Hut: complete invincibility was not a feature of the original design, for a 3rd level slot. I understand the intent, but I've also seen the "force field" feature used to bypass walls of cursed fire, etc. Next campaign (I don't like to create uncertainty with groups by announcing changes every week), it's going back to original design: a bubble that protects against temperature and gases but that's it.
Forgot about this one! I rule that the hut keeps you safe but that you can't attack anything outside of it. There's basically an "inertial barrier" that stops arrows and other missiles just like spells from inside the sphere. So shoot an arrow from the inside and it will just fall once it leaves the hut.
Supposedly that was the intent of the spell, protection for those inside, unable to attack anyone outside.