I guess if you wanted to use DEX and didn't want the crit than the Topaz Rings with Parry would be a better choice.
Yeah, the Ruby accessories are great, as extra damage/enmity is always welcome even for PLD.
DEX for PLD is better than parry as you gain Block and Parry.
~0.066% per DEX into Block/Parry
~0.076% per Parry Stat into Parry
so about 4.5% extra block or parry. Also, block % is higher than parry % - and Block takes priority during frontal damage.
Not great but it's something. That's why I'm hoping we get new accessories with both stats, so you can have the extra damage, vit, and small % to Block/Parry.