Festerblaze aldready has 12% phys res on 3 piece bonus. Stacking too much phys res on Blue sets are not productive I think because they are meant to be placeholders for mythical gear.
Did you check this build out btw? Apostate: Festerblaze Set - Fire based Ravenous Earth & Rune Of Kalastor - SR 75-76 / Cruici 150-170
I am phys res sucker and shield adds additional AoE to it