Parry is not a worthwhile stat when "average mitigation" doesn't matter because "avarage damage taken" doesn't matter, base parry rate is already sufficient, and needing so much parry to give any return makes it not worth investing in.

As a tank, the only things that ever threaten your HP total are huge attacks like Mountain Buster, Death Sentence, Ravensbeak etc or a bunch of attacks from multiple enemies intended to be tanked separately (T7 Melusine+adds, T8 Avatar+Dread, T9 Boss+Ghost) or a big dungeon pull.

For these situations you never rely on your random mitigation (block or parry). You always pop an important cooldown like Rampart or Sentinel (or Inner Beast as WAR with some other cooldown additionally). Your healers cannot "underheal" in anticipation of a block or parry because you will die. Therefore when you parry or block you usually cause overhealing anyways. If you die from such a big hit due to not parrying or blocking it and you popped cooldowns, that's a fundamental problem that you and your healers must fix somehow by mitigating it better. Parry won't fix it.

Falling into the pitfall of "it's a mitigation stat, I'm a tank" is short-sighted.