I used just one dagger and some expertise rating to avoid misses and dodges/parries which would affect the results. Each test includes 1000 hits.
Improved Poisons talent : 10% increased chance to apply poisons when attacking the enemy.
Without the talent (30% chance to apply poisons)

With the talent (40% chance to apply poisons)

Seems like this talent works just fine. I was actually suprised that I got exactly 100 additional Wound Poison procs after doing the first 2 tests. The amount of resisted poison procs seems to be low enough and correct with the 1% random resist chance for spells to resist, characteristic for TBC.
Resistance tests:
VS Paladin, 0 nature resistance

VS Paladin, 71 nature resistance (Improved Mark of the Wild 2/5 28, Flask of Chromatic Wonder 35, Broiled Bloodfin 8)

VS Shaman, 236 nature resistance (Nature Resistance Totem 70, Flask of Chromatic Wonder 35, Broiled Bloodfin 8, The Natural Ward 35, Pendant of Withering 30, Cloak enchant 15, Shield enchant 5, Nature Resistance racial 10)

Seems like the famous rogue with 20 spell penetration enchantment on his cloak had some plan when he setup his gear. Wound Poison appears to be highly dependent on the nature resistance and this might be the reason why it resists to much in PvP. Crippling Poison is even more likely to resist with all those effects like Hunter's 15% snare resist talent or just simply Surefooted enchantment.
Is there any addon to test Vile Poisons 40% chance to resist dispel effects? I simply used recount but it doesn't really work good enough to test dispel chance. My addon just counts direct dispel effects like Cure Poison, Cleanse or Abolish Poison (the direct effect of this spell), but doesn't work for Abolish DispelOverTime effect, Poison Cleansing Totem or not even for direct totem dispel effect.
Could someone please suggest some addon that could solve this problem and measure dispel attempts correctly?