[PvK]

I think a longer weapon will avoid poisoning from coral armor.

In general, yes, I think luck and twist fate would help, though perhaps not against attacking something with poison armor using a short weapon.

The results of poison, being on fire, etc. will continue to be resolved until the situation is corrected by the afflicted units (i.e. there's a chance each turn the poison will stop having effect). Naturally, the defeat of the enemy doesn't help against poison already in the veins.

PvK