I finally got around to parsing some of my test runs. The lag's pretty bad -- this was off the 2.2 PTR after all -- but I've got a lot of data. It looks like main hand attacks get the parry haste, and off hand attacks do not.
These are using two 2.7 speed swords.
MH:
[Protector's Sword]
OH:
[Protector's Sword]
