I mean, of course they do stuff, but are they worthwhile enchantments at all? I have a war axe that should obliterate an enemy's stamina and magicka with one swipe, but vampires I've fought will still cast spells after I've hit them.

In Oblivion, negative stamina would cause enemies to ragdoll. Not in Skyrim, though.

So are these enchantments worth it? If not, what other non-lethal enchantments are worth using?

Probably not absorb stanima would be far superior as it at least gives stanima to you and NPC mages tend to have a few hundred magicka and low cost spells. (oddly enough dragons can't use shouts when drained of magica).

Stamina drain is good, it disables enemies' power attacks for a while. Magicka drain is only useful on dragons, 'least for me. NPC mages tend to have impossible magicka pools.

Here's the problem: Drain health-bar works far, far better. For that matter, why drain stamina when you can do cold damage and drain stamina for free?

What do you mean by that last bit?

I learned from oblivion that damage magicka doesn't seem to do much to mages attacking me.

Skyrim added stamina to magicka, damage both still does not seem to do anything.

I now just use absorb, at least now I get to recharge my stats...

Thing is, using the resto loop I wanted to make an "über" weapon, just not one that would one-shot. So I opted for auxiliary enchantments instead. I suppose absorb might be better, at the very least.

Probably that Frost does both Health and Stamina damage... though an enchanted weapon does, too. But Frost is still the mage's ultimate weapon against big brutes.