Everyone's "most kills" are against warriors. That's simply because warriors are the most popular class, hands down and have the least defense/utility (no hide, no heal, no dam redux).

I tend to agree that the iron poison dagger is stupid. I dislike the idea of the popularity of that weapon. The poisoning sword isn't as much of a big deal since sword specs don't have any other maledictions to stack with it.

On the whole though I don't find dagger specs any scarier than whip, axe or sword specs - depending on what I'm playing. As a shaman maybe, but that's obvious because shaman's are based purely on maledicting strength which is moot when the user can never drop their weapon because of strength loss (less than 3lbs weapons). Likewise they don't get dagger, bleeding hampers them a lot and they can't lag. Its pretty much a shoe-in for an easy victory for the dagger spec.

That being said, on the whole, dagger specs don't scare me very much.