There's also no save DC listed for the poison, just the number 5. Looks like if you get tagged by the Spine Attack, you automatically take 5/damage per round are slowed until cured. Nasty effect.
If Poison does damage over time, that would explain the old blog comment about Warforged DR not defending vs poison.
Oh, would also tie into "after-effects". After all, if you're still taking 5 hp every 6 seconds outside of combat, you're pretty much insta-dead. Poison may have a different crippling effect outside of combat.