Hmmm there are several long threads on this with Parcer showing extensive testing. I would try and give them a look up. Since they are extremely detailed and all the answers are there. If I have time to find it ill link it. Quick idea. It procs all the time almost immediately its stacked in pvp. each enchant can proc multiple times. 6 enchants procing 9 times. etc... its all in that thread.
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