D&D is an RPG. A role playing game. Characrters play a role in a story.
In stories, some tools are more useful for certain things than other tools. Some tools give you great protections. However, if there is a tool in a game, it is often there for a reason.
In
most of the games I experience, Tiny Hut comes into play. So much so, it is an assumption on my part that once PCs hit 5th level, I'll see the hut either as protection for my PC in the game at night, or as something the PCs will use to protect themselves in the games I run.
As a DM, I do
nothing special to account for it. Wandering monsters will come across it and treat it as I think they would based upon their intellect and knowledge. Crafty and magic savvy enemies might set up an ambush, but a T-Rex might bash at it a few times before leaving.
I have never, not even for a second, found this approach problematic or disruptive.
Remember that our heroes are ... well ... heroes. They should feel like they can do things that matter. This spell is an example of being able to do something very useful and powerful that makes heroes feel like they're more than a typical peasant. It is a good thing.
I will say that if I were to redesign this edition I would make a couple small changes:
- I'd move it to 4th level as a spell. It would be better to have the PCs not have quick access to this at 5th and 6th level. I'd like to stretch the time without this protection a bit - but not much.
- I'd clarify that it has a floor.
- I'd give it an AC and hps, as well, so that it can be beaten down with a lot of effort. This isn't about making it less effective - this ia about adding the "Star Trek shields are failing" scenarios to the game. It would likely have a regeneration ability that would continue to function, even after it is pierced.
- I'd reduce the casting time to 3 rounds. This is a spell that I want PCs to not be able to cast casually in combat, but allowing them to struggle to get it up in combat when you need that defense is a good dramatic option. 3 rounds strikes me as the right sacrifice to get your shields up.
- I'd require that nothing block the shape of the sphere. You need to have a break in the dungeon, in the trees, in the hillside, etc... to make room for it. That makes it a "goal" to find a safe place to camp in some environments.