Just to theorycraft for a tad, Killedar shield will give you (50% + 30% from DEF/2 with +6% from Shield defense bonus at 99 PLD) a total blocked damage reduction of 86%. Blockrate will depend on what you're fighting, but mostly will be around 40%ish for a Size 3 against most opponents of worth.
Unless it has a hidden increased blockrate, it's not going to compete with either Aegis or Ochain. With a PDT set that already caps you, this will offer you very little extra.
Typical showpiece until someone claims it blocks like an Ochain again or blocks all of the damage like someone did with the Steadfast shield before :/
