Are my mitigation numbers off ?

[Reynhart]

Using average mitigation is a flawed way of looking at how things work in practice

Average sustained mitigation doesn't matter in this game.

Yes, you're right.
There is just a tiny little bit of a problem with this.
PLD most definitive tool is its shield...which provides...average...mitigation.

Not having a shield doesn't prevent you from having mitigation skills so, the fact that Bulwark or Sheltron use it is just cosmetic.

So again, one of the claimed definitive advantage of PLD is, at best, flawed, at least, a blatant lie.

Damn quota....
Answer to below:

Its boost to block rate is significant enough to be reliably useful when pulling a large amount of mobs in dungeons, for example.

Yes, it is.
But dungeons are hardly challenging. And for larger pulls, Bloodbath+Spam-Overpower or Blood Price+Spam-(DA)Abyssal Drain provides far more "mitigation" than Bulwark.
Without talking about the AoE enmity and damage gap...