Pros:
-Breaking the attack/block/attack rhythm(doesn't really break it, just adds a few instances that will cause people to block twice).
-Adds risk to holds, which were by far too effective for how little risk there was/still will be. Likely this will buff chamber attempts.
Cons:
-More defensive playing. Increased risk disproportionately while maintaining either the same, or lesser level of reward. Further solidifying the necessity of high armor among melee characters.
-Ping fluctuations being greater than the window of opportunity for double hits. My ping in the mornings (When I prefer to play) is about 30-35, my ping at night is 70~. So learning what the threshold looks like for .03 seconds in the morning, will result in my receiving more double hits in the evening.
I suggest increasing the window to .05 seconds at least so that it feels less random. The more concrete a thing seems, the more likely players are to adapt to it, rather than pass it off as just a random occurrence. This will slow combat down further, but increase depth ultimately. There will always be ways to speed combat up, and a new wpf formula can help with that.
I disagree with the Inertia pro, not because it isn't true, but because it's only there due to the inability to block and attack with the same motion, aka game mechanics limitations.