There is one thing to consider, and I'm setting it in a separate post so that it is not confused with the above point.

It's possible that at a certain level of Dex/Parry that 100% of hits taken could be parried. This would effectively change Parry from Avoidance to Mitigation. With the current numbers I've seen, I highly doubt this is possible in reality, however I have noticed that the increases appear to be linear with no current sign of a soft cap or built in diminishing returns.

That would then cause Parry to effectively increase your EHp against physical damage mobs, and would make it acceptable to rush stack Parry/Dexterity to reach that point. This would be similar to WotLK era tanking where you first needed to rush avoidance to remove crits off the table before stacking HP.

Which brings up another interesting point, and that is has anyone done any testing with high amounts of avoidance and crits taken?