Honestly no one is really sure their card is "Defective" really aside from a few. The black screen crashes don't 100% mean your card is defective, could very easily just be drivers or bios issues. A lot of it is failed over clocks.
My advice would be to run it on air for a little while and if you don't get black screens on stock settings you're probably alright.
I most certainly wouldn't dismantle the card right out of the box since no one is quite sure what the black screen crashes on stock clocks means.
Good luck if you do!