I've been experimenting with a 2 chambers pit (inspired by a recent QPTech video, link in the spoiler below)
One chamber is for the mobs, a 3 deep, 2 wide trench dug from the surface (with flowing water to push mob/corpse/items toward the player area).
The water flow system is optional.
it is a simple 1 wide, 3 deep trench that extend 1 more tile on each side than the lenght of the pit (so that the water can flow everywhere).
Put the water on 1st block dug from the surface and cover with a slab to prevent mob from falling in.
The blocks at the pit floor level are removed to allow the water to flow and fences are put at the botom layer to prevent mob from trying to flee in the water way).
the player chamber is 2 high, 2 wide with floor tiles occupied by your favorite antispawn item (camp fire, branch layer, ... whatever works for you).
the interface between player and mob chamber has a bottom row of fence gate (choose your style).
the second row is alternating a single fence (attached to the ceiling) and vertical slabs (which the fence post does not attach to).
NB: the spawn prevention look like firepits because of the instant firepit mod, dry grass should be enough (easy enough to include a safe room in the design just in case).
in there you're protected from projectiles (stone or bowtorn javelins) though if you stay too close to the fence gate, you're vulnerable to melee (hence the 2 wide player area) and can reach around the fence post to attack or loot corpses.
if you hug the fence gate, shivers and drifters will be attracted to you and jump in the pit.
I did not see bowtorn fall in during the only temporal storm I had to work with. (wandering or getting in position to shoot you should make them fall in eventually).
I would recommand to close the entrance with a block rather than a door or fence gate to prevent mob from camping the entry/exit.
The design is modular, you can extend it with as many segment of slab/fence/slab as needed (bigger = better mob spread, less chance they'll kill each other).
it's pretty fast to dig one if you have the materials at hand (6 stones, 2 clay, 14 sticks).