Netgear Readynas killing my drives

FWIW, I always test mine with Seatools before adding them to the NAS - doing both the full non-destructive read test, followed by the full erase test (simple overwrite).  I've sometimes purchased out-of-the-box disks that pass one of these two tests, but fail the other.  And from time to time I've received a batch of bad drives (I suspect due to mishandling during shipment, but of course there is no way to tell for sure).

So I wouldn't assume that the NAS was "killing them", as it is quite possible that they were defective to begin with.  Especially if you are seeing these issues in more than one model. That said, ATA errors can be tricky to isolate, as they can be a result of issues with the SATA backplane. 

I'd start testing them with Seatools, and exchanging ones with errors with the seller.