The parry rate of 73's is at least double their dodge rate.
I agree it certainly doesn't seem like the same number as dodge. I believe Lv. 73 NPC dodge has been figured out to be a little over 5%... but I keep looking and I can't find anyone that has calculated exactly what NPC Parry is. I seem to get numbers all over the board when I test it, although 9% might be a good number to use based off Fame's logs.
So we still need to know the exact parry number to calculate a Cap... but I think we know you at least get diminishing returns after your target can no longer dodge (22 Expertise), as each point is only effecting parry.
I think Fame came up with 22 expertise rating = 1 expertise point.
No, pretty much everyone is saying the conversion is the same - 22 expertise rating = 5 points. Making it pretty damn good (better than + hit for threat gen while also reducing spike damage via parry reduction).