PLD 4.0

[Reynhart]

Given that it guarantees the block though, I don't see how this would be a fair test.

Sheltron doesn't really guarantees a block. It only makes you Block roll 100% succesful.
If a parry roll can go unrestricted by block, it means that, sometimes, you would do a successful parry roll even with Sheltron up.
If you never parry, then the parry roll is restricted by a failed block check, making them dependent...and making your parry rate unaffected by the size of your shield a bit strange.

For my last sentence, it means that a critical hit will bypass Sheltron, not activating it.

As for miss...Actually I don't recall ever seeing an incoming "Miss" instead of a "Dodge", so I'd say that's a single accuracy/evasion check. Feel free to correct me if I'm wrong on that.

Another option would be for RA to simply ignore the dmg penalty of Shield Oath.

Simple, subtle, elegant.
Thumbs up !