Yeah, I think Byrth is onto something. Check damage when you know you're capped attack, without PDL gear. Add PDL gear and see if you break the "cap". Wouldn't shock me to see this stat just increasing the cap, meaning the subjective value is going to depend highly on whether you're often fighting things when attack capped. Then, also check when known to be uncapped and see if anything changes with/without PDL.
Also beware of spreadsheet biases when people start theorycrafting this stuff, since some people here like to assume everyone has perma-capped attack and is running around with Bolster Fury/Frailty + Chaos Roll + Honor March + Minuets + Berserk... which might be less likely to be true in practice on a difficult mob. Comes down to whether you're seeking to optimize for content where you're capping atk anyway (meaning it's maybe just speeding up something you're probably rolling anyway), or gearing to beat hard content that you're far less likely to be capped atk on even with realistic buffs (say, Divergence wave 3).
Im thinking the same as Byrth. Which makes me question this augment on BRD neck, but less on DRK neck.
I questioned it on PUP neck too. I guess maybe trash mobs? But... eh, that doesn't sound so hot.