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It isn't viable solution to immunes.
You must be aware that if skill breaks immunity, its -res effect only applies with 1/5 effectiveness. So -25 enemy physical resist * 1/5 is nothing. Even if it was full -25%, theyd be still at +75 res, which would make them insanely tanky. You'd need another skill that lowers phys res by a huge amount.
Back in the day, retal pala was great in fauzt. Plague damage was very high (similar to curare), so that alone could melt them very quickly.
Another thing that helped, was gigantic range, so you were poisoning much more enemies at same time.
Currently I think only way to clear them fast as retal pally, would be to get punisher procs form sssu holy lance. I don't see any other procs nowhere near as strong as this one.