.. that OP alloys will resist much better than normal alloys.

The a'dam is made of silver, but not really silver anymore. It's an AOL-style silver-based metal or matter of unknown name, no doubt with matrices for saidar and what not in its molecular structure, as it is after all a ter'angreal producing very specific effects.

I get the feeling they'll prove resistant to Shai'tan's attack (at least away from SG), as OP forged weapons most likely will (that may have been one of the purposes to use the OP in their making in the first place. All WOS era weapons we have seen are OP-forged).

Also, don't forget one thing: it's been confirmed by Maria Simmons the melting metal was a completely localized (so Bubble of Evil-type) phenomenon.

We may well see that again, and once the seals are broken it could get far worse, but there's still no certainty it wasn't a random corruption of reality's laws that the DO is not at the moment capable of reproducing at will anywhere he wishes.

Of course that's just theory, we won't know for sure until the book is out.