I just took zombie fighter with my shifter, and then noticed that the helpfile specifically says "allowing for such attacks to be PARRIED with greater ease" (emphasis added). So does that make this edge totally worthless to a shifter while in form? Or does it actually mean AVOIDED with greater ease and the helpfile is simply inaccurate? And if it really is specifically PARRIED, can it be made to be useful to shifters in form as well? Since few if any shifters will ever use the parry skill at all while in form.

It means parry as the helpfile says.

It's an edge you can pick as a shifter, but unless you fight unshifted a decent amount you probably don't want to.