So I've been hearing a lot of opinions and it has been pretty unanimous so far that the best stats for a PLD are accuracy and parry. However, lately, I've seen a few people claiming parry is far worse than most people think on the PLD because you can't both block and parry a single attack (which I already knew) and stuff you could be blocking you have instead a chance to parry it (blocking is better since it not only mitigates more damage but activates shield swipe).

My question here is...how does the parry/block REALLY work?

I've heard stuff like:

1.Mob hits paladin.

Game rolls to see if hit is blocked. If roll succeeds, hit is blocked. If roll fails, game proceeds to next step.
Game rolls to see if hit is parried. If roll succeeds, hit is parried.