I'm struggling to justify using this enchantment.

Most of the time, the magnitude is fairly small. Currently I've got Bolar's Oathblade, which damages around 35 Stamina per hit. But NPCs have pretty large Stamina pools unless I'm mistaken, meaning I'd need to hit them several times before it reduces their Stamina to zero.

Since you only need 1 point of Stamina to do a power attack, it would seem there's no point in damaging an NPC's Stamina unless you get to zero - and even then, they'll get it back in a second as it recharges automatically. And even aside from that, they could still do normal attacks.

Can you get NPCs' Stamina into the negatives, to actually prevent them from power attacking?

Can you combine Damage Stamina with any other Stamina effects (Ravage Stamina, e.g.) to get something useful to happen?

Are there any other uses to Damage Stamina enchantments that I'm missing?

The enchantment would have to be pretty high. Stamina is important in the early goings where 4-5 swings can cripple you, and sprinting for more than 2,000 units(or about half a cell) will empty your stamina, but as you level up and get a bigger pool, Stamina becomes meaningless. This is even more evident with NPCs, as their stamina regeneration appears to be higher than the players(NPCs power attack like no one's business).

If you really want to screw them up, you want an enchantment(if possible) that reduces total carry weight. Or something that makes them over encumbered. You can't run while over encumbered and this applies to NPCs.

Either that, or damage stamina + damage stamina regen. So, you take it away, and it STAYS away for a bit.

Unless you are intentionally reducing the damage you inflict, most fights won't last long enough for reduced stamina to make a difference. Boss fight are, of course, a different problem, but even they become trivial as your PC levels and perks.

I don't believe there's a way to over-encumber NPCs.

Personally, I find the drain-health enchantment to be the most useful on weapons that are used by mages or rogues.

I loved Stamina in Morrowind. Unarmed attacks reduced stamina and when it hit 0 the NPC (or you ) would fall down until you recovered enough to get up. It was fun to punch a troll until it fell flat on it's back, then wait till it got up and knocked it out again with one punch. I really miss that. I don't think stamina really does anything much in Skyrim.

First thing I do with all my characters is buff the hell out of stamina.

It's best paired with damage stamina regen poisons.

Creep cluster and wheat can be used to make it.

There is a way to get a huge stamina enchantment if you have 100 enchanting. If you also have augmented flames perks in destruction then combine fire and damage stamina on a weapon it ends up being a large number which I don't remember. Something like 70 or 100 damage stamina. Combine that with damage regen potion it should do something. I didn't test it though.

What happens to a NPC in Skyrim whose stamina is 0?

AFAIK, absolutely nothing, except they can't power attack (in theory). However, I've read that NPCs who can't power attack will still use the power attack animation, so it can be hard to tell.

That's the problem with damage stamina, I guess.... In theory, you'd want to use it against tough, hard-hitting enemies so they couldn't PA against you.

I'm curious if anyone has tested the Damage Stamina Regeneration route, combined with Damage Stamina enchantments, and actually seen a useful result.

It is pretty useless, as everyone and their mom can do power attacks with like 1 stamina point or so.

I've been playing with Requiem mod installed, and stamina is a huge focus there. Without it you or the enemy is dead. Hence, i no longer leave home without a damage stamina poison.

Damage regen poison and damage stamina enchantment. It gets ridiculous when you have to use two crafting skills just to get an enemy to stop power-attacking. And we still can't be sure that works. Hope next game has more effective ways to attack NPCs attributes.