I've seen varying damage as well (v0.85).
I've got a Champion with poison dagger +4, sac +1, and vial +2. I haven't paid it particular mind; but I think I've seen as high as 6 damage from the dagger... [after a strike I'll see the weapon damage displayed, followed by three more damage values that I presume to be the poison]. I've definitely seen greater poison damage than 1. And saw it before I'd gotten the +2 vial. I've got a couple other champs with sacs and vials, and the assassin champ originally had a +2 dagger. So even though I haven't paid particular mind to this question, I'm fairly sure I've seen the dagger damage being applied as a value greater than 1.
It seems to me that poison damage should act as a status affect rather than as a weapon buff. But there are balance considerations I might not see.
