Ah, thanks for the clarification!
That makes Hydra MH proc damage significantly decreased in that case.
EDIT: Apologies, I read your initial post on the bnet forums wrong, hah! Mustve been out of my mind.
Here's the link if interested:
It is labeled as PTR only, meaning it doesn't exist on live. The issue was an internal bug fix that was never exposed to players. That being said, they did change something to fix it.
sVr did some testing, and found that nothing appears to have been changed with paralysis / MH proccing, it still scales off of AS for both damage and cast rate.
My best guess is that it might have been the core skills' damage (the hydra itself) and not the MH proc that was wrong.