seems normal poison must make contact with skin and u arent hitting skin unless shield is off unlike gas that has to be inhaled and a shield wont stop that

It's weird because poison from Tai attacks and chases goes through shield like Shizune or Kankuro, they should use same rules for all poisons honestly.

Kinda what Dym said, if that's the case why does Kankuro's puppet apply his poison on standard, or just his actual standard without puppet?

The poison via 'Poison Tai' passive only works if you can *e the shield and do damage to the actual health.

He's correct. It's not bugged. Poison Tai still does dmg if you have Tai *ion and deals some HP. It will work as long as the enemy HP got hit even a little.

If you play against Earth main, better to have Karin or Kankuro in your team, their poison goes through shield, because it's ninjutsu, also try to acupuncture Earth main to stop him from shielding team.

it's bugged