I just tested out Misery, which is for shields, and that works fine:
http://www.youtube.com/watch?v=OIPLMcHzrNo
Procs off blocks (7 seconds in, it's the black aura and sound effect), but the damage otherwise sucks. I guess if you have it you might as well use it since that's free damage, but other enchants would obviously be better.
I also have Suffering on my weapon, but I tried 0 normal slashing him the rest of the way and didn't notice any animation for that, if it even went off. I thought at one point during an Irukul fight that I had gotten it off, since he was bleeding a lot, but I couldn't tell if that was because of a Bloody Thread or not (I forget if there's a lingering blood animation from that).
I can't imagine Suffering being any better though, since that's a rank E enchant, while Misery is D.
EDIT: I think Suffering does work. I've seen the misery effect proc on some bosses when I solo them, even though I don't have my Horn Shield equipped (my Knight Shield doesn't have misery).