You missed the biggest part of the nerf anyways.
old: for each Affliction effect on the target
new: for each of your Affliction effects on the target
So now each of your Warlocks will need to put up 3 Affliction effects -- probably CoA + Corruption, Haunt, UA and Shadow Embrace also count... not sure if drain life counts towards itself or not? to get the full benefit.
On the other hand, the Siphon Life change is a nice boost IMO, Eradication no longer has a cooldown, and they lowered to 30 minute cooldown on Ritual of Doom. So you could have 5x Doomguards out for 50% of the time :~D
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