So...
The Pho? Wut are these shenanigans!
Minor difference between 5* minor and strongest poisons (<10 damage) (The * power of a weapon may affect poison, need a Toxic Vaporizer to check)
Plague Needle normal attack poison is less effective...
Vile Striker normal attack poison has same potency as Plague Needle Charge attack
Single damage weapons get [crappy] bonuses while split damage weapons get significantly more... Antigua update!@#@!#!
Halp me! T.T
Poison reduces defence. Since split weapons are affected by two defences, it gets a bigger boost from two defences being lowered. Plague Needle's normal attack probably only does moderate poison instead of strong. Many weapons have a weaker status on the regular attack instead of the charge. Fang of Vog, for example. Which depth are these numbers from? I can reveal that, at depth 24, poison should be the most effective for nornal damage r weapons that do a bit less than 131. Not as effective as split damage weapons, but still pretty effective.
The most effect you can get out of poison is by using a split damage weapon that does a bit less than 262 against a neutral target. Multihits are good also. Combine with Deadly Shard Bomb.
I have tried toxic vaporizer and venom veiler on T3 sandbags. There is a difference, but it was incredibly small. We're talking 1 damage point here. Minor poison seems to reduce defence by about 15% while strong poison reduces about 20%. For some reason, moderate poison is closer to minor than strong.