I dont think that pass block OL can be effective in regular leagues not only because they dont seem to be better pass blockers, but because they definitely are terrible run blockers and regular teams cannot seem to be successful with an all pass offense.
Heavier passing offenses are apparantly easier to pull off in casual. I think that it can be done there.
Most pass block OL I have seen are not built very well and have crippling strength, as well as play for teams that dont only pass. I could build a replica OL to the ones on my two PL teams (with 155 strength, and have done so in the VPB many times), where the only difference would be putting the SPs from 10 RB & GL into more pass block SAs. Unless Max Protect, pass block focus, and pass block SAs do not work, it seems impossible to say they would not be at least slightly better pass blockers. That would probably only work for an all passing team though.
Im curious what the best all pass block OLs have looked like, and what teams they have been for. I was intending to try this out on a casual team I will make in the next couple seasons.