Probably not very, as the OP is talking about real physical defects. Bad sectors is a defect, yes, but it's more of a filesystem one. The undersides of the discs shouldn't have nasty scratching or dye leak problems if it was just copy-obfuscation-intended bad sectors (although bad sectors is almost certainly a result of the faulty pressings this thread is describing).
And I'm wondering whether the recent ISO decryption method posted in this thread on Doom9
that I helped troubleshoot for MinGW would solve this issue with ripping Funimation discs. I don't own any myself and I'm unsure of which ones count among those my sister owns, so I can't say. Works fine on regular discs, though (I tested it with Toradora!, which has no sort of bastardized encryption on it).