2 healing prevention per level... Apheelsik is 10 and Gorgon passive is 5.
Definitely item slot efficient, but not gold efficient at all. And almost any item that increases your damage output would make a bigger impact most of the time. When you apply such a small amount of poison, the use case is naturally edgy - it's either not anywhere near enough to make a difference, or you didn't need poison to begin with. At least with the glyph there are way more cases when you can apply poison faster than they can recover from it.
Was this tested at other values, like 3? I could be wrong about this, but I've seen the same remarks about Venom Dagger being mostly bad elsewhere and nothing to the contrary. Sure, it's good-ish for regen fighting, but Platemail or Martyr Wraps seem to outclass it by a lot. You might be able to make it work with Halpmeh, but I have doubts even then.
I'd maybe pay 10 or 12 for the current version, but more poison would be more satisfying than a lower cost.