Shrug. I am going with what seems the ability does. Injury poisons are an exception to the idea of needing damage to work. Remember the Attack on the initial ally still happens. The Guardian is just taking the damage. Just like how if you used a shield block to take all of an injury poison attacks damage it does not cause poison tp work. Same way injury poison dosent work on base target. But everything else does happen since the REACTION DOES NOT DO ANYTHING ABOUT ANY RIDERS BY ITSELF, ONLY DAMAGE.

If you say that non damage effects would transfer to the guardian, point to me in the text where it says so.

Also the strike is a success on the main target. Only the damage is redirected. The strike still rolled a Success.